Version 2.0.0

[Summary]

BuildMaster is a small CMake DSL for a graph of other people’s builds.
You declare each dependency once — how it is produced, what it waits on — and the parent gets one shared prefix instead of a pile of ExternalProject / FetchContent glue.
CMake and Meson trees are first-class.

Typical use: add the submodule, add_subdirectory, declare components, then depend / link.
Declaration order does not matter.
The public surface is ten commands on purpose; everything else is internal.

If you landed here from a release link and have not read the tree:

• How to write a component, every optstr key, and the contract: README.md
• The ten names, and nothing else: public_functions.md
• Porting an older caller: MIGRATE.md

2.x versus 1.0.x is a different product: declarative graph, no generated fragment to include(), no public dependant factories, no public create_cmake_component / create_meson_component.
A 1.x CMakeLists.txt will not configure.
That is the point.

What 1.0.1 already did internally (headers mode, per-component toolchains, nested binutils, env runners) is still there; the caller and the declaration shape changed.

Added

• Declarative component graph.
  buildmaster_depend(source dest) is order-only (id, stage name, or existing CMake target).
  buildmaster_link(source dest) waits and records the same depend edge, so buildmaster_link(A B) before buildmaster_component(B) still defers A.
  dest may be a component (all produced libs), a library spec (name / subdir/name), a target, or an archive path.
  Spec dests are listed on the source install OUTPUT so Ninja has a production rule.
  A spec or on-disk archive stays link-only.
  Duplicate explicit edges are WARNING + no-op; internal auto-deps do not warn.
  Unresolvable dest at finalize is FATAL.
• Deferred materialization + eager INTERFACE stub.
  Registration only stores metadata.
  Fragments and stage targets exist at the end of parent configure (cmake_language(DEFER) on CMAKE_SOURCE_DIR).
  Declaration order does not matter.
  Components without edges still configure during parent configure; components with edges configure at build time under <id>_configure.
  add_library(<id> INTERFACE) at registration so a sibling ALIAS / target_link_libraries before DEFER does not see a missing target.
• buildmaster_component.
  Backend is inferred from srcdir (CMakeLists.txt vs meson.build; neither + headers → none).
  Dual markers are FATAL unless BACKEND=cmake or BACKEND=meson (allowed set: BUILDMASTER_FACTORY_BACKENDS).
  BACKEND= empty or an unknown name is FATAL.
  SOURCE=<rel> is applied before that detect: the value is always under the positional srcdir (a leading / is still a child of srcdir, not an absolute path).
  Escape above the component srcdir (or above the host CMAKE_SOURCE_DIR) is FATAL before any existence probe.
  After the boundary check, a missing directory is FATAL.
  The resolved tree must contain a .git only when GIT={…} is also set; SOURCE= itself is not a git root.
  Arity is id title srcdir options mode produced [optstr].
  Mode is static, shared, headers, or executable.
  options is a backend-agnostic CMake list of KEY=value (a single string is one pair).
  Idioms CFLAGS, CXXFLAGS, CPPFLAGS, LDFLAGS, INCLUDES, DEFINITIONS are rewritten for the nested compile and append to the parent job / toolchain.
  Every other key is forwarded as -DKEY=value to the nested CMake configure or Meson setup (Meson also uses -D).
  A leading -D / -d / /D on the key is stripped.
  Private to that nested step, not INTERFACE.
  none ignores the list.
  none outside headers mode is FATAL unless NOINSTALL is set; a unique backend is still used when present.
• Mode executable.
  Produced specs are binary stems under BUILDMASTER_INSTALL_BINDIR (<stem> on Unix, <stem>${CMAKE_EXECUTABLE_SUFFIX} on Windows; never .exe.exe).
  The parent stub is still add_library(<id> INTERFACE) — it is not an IMPORTED executable.
  Nested CMake/Meson build the binary; LINK / LINKFLAGS apply to that nested link.
  Linux gcc/clang: nested and parent CMAKE_<LANG>_LINK_EXECUTABLE wrap <LINK_LIBRARIES> with -Wl,--start-group / --end-group so a static exe that lists provider before consumer (ld.bfd single pass) still resolves, including under LTO.
  Darwin ld64 and MSVC/clang-cl do not get those flags.
  SHARED/MODULE recipes are unchanged.
  WHOLE on the executable itself is INFO and ignored.
  A leaf of a WHOLE meta is the same INFO skip: the meta must not emit -WHOLEARCHIVE:<bindir>/<stem>.exe / --whole-archive of the binary.
  STRIPRES does not run.
  PC={…} ENABLED is FATAL.
  REPACK on the executable itself is FATAL.
  A first-level depend/link dest that is executable is not a REPACK member (INFO skip; not FATAL as a “publishing member”).
  A leaf of a REPACK meta that is executable is the same INFO skip and is not an INPUT of the merge.
  Extra buildmaster_link dests that are raw library specs are not folded as IMPORTED archives on an executable.
  Produced exe stems are never BM_LINKS_LIBNAMES and never land on a consumer or meta link line (gzip.exe is not a library).
  Membership in a meta is order-only (*_install).
  Oficios: rename_executable (when RENAME) then outputs.
• Assigned build directory.
  There is no public builddir argument.
  The graph uses ${CMAKE_CURRENT_BINARY_DIR}/bm/<id> and file(MAKE_DIRECTORY).
  The path is an internal property, not part of the DSL.
• Outline groups.
  buildmaster_group(id [title]) and buildmaster_group_add(group member…).
  A group is not a component, a meta, or a link: no targets, no edges, no install.
  After the graph is complete it only walks members in addition order and prints configure banners with indent.
  Nested groups are allowed; a member must not contain a group.
  Cycles and id clashes with a component/meta/group are FATAL (caller file:line).
  Configure-time messages inherit the walk indent; compile/install stay flat.
  Eager vs deferred is unchanged — the outline is cosmetic order, not a wait edge.
• Headers island (mode headers, with or without a backend).
  No backend, or NOINSTALL headers: private.
  Direct consumers get a quoted -I on that id’s nested configure only (CMake CMAKE_{C,CXX}_FLAGS and Meson c_args / cpp_args).
  It does not recurse through further BM components, runners, or INTERFACE.
  Publishing headers (backend + not NOINSTALL) install into the shared prefix; the prefix -I already covers them.
  Several private islands on one consumer accumulate several -I.
• FILES={URL=…;NAME=…;UNPACK;SOURCE[=rel];FORCE;MD5=|SHA256=|EXPECTED_HASH=…}.
  Declarative download on buildmaster_component (meta + any FILES group is FATAL).
  Always cached under BUILDMASTER_DOWNLOADSDIR (FORCE refetches).
  Unpack is ${BUILDMASTER_BINDIR}/files/<NAME>/, before nested configure (eager components included).
  Inner SOURCE (at most one group, requires UNPACK) is the srcdir after unpack — the positional path is ignored by design (WARNING).
  That key is not the component optstr SOURCE=.
  Other unpacked groups inject a private -I on that id only (same rule as the headers island).
  GIT={…} + FILES SOURCE is FATAL.
  Replaces the 1.x file_download* + dependant-component pattern.
• LINK= / LINK={…}.
  Raw system linker names on the component or meta INTERFACE.
  They propagate to whoever links that id.
  Not BM nodes.
  Revives 1.x LINK_EXTRA under a shorter name.
• LINKFLAGS= / LINKFLAGS={…}.
  Raw linker flags (/FORCE:MULTIPLE, -Wl,-Bsymbolic) for the nested cmake/meson link only.
  Groups: WINDOWS, LINUX, MAC, UNIX (UNIX = Linux + macOS).
  A group that does not apply is skipped at INFO.
  Unknown platform key is FATAL.
  Folded into that id’s OPTIONS at finalize (CMAKE_EXE/SHARED/MODULE_LINKER_FLAGS or Meson c_link_args / cpp_link_args).
  Not target_link_options on the INTERFACE — a consumer of this id does not inherit the flags.
  Meta: WARNING + ignore (no nested link).
  Headers: WARNING + ignore.
• GIT={FETCH;SWITCH=<branch>;RESET;PATCH=<file>;ROOT=<rel>;TITLE=…}.
  Srcdir git work on buildmaster_component.
  ROOT= is always under the component srcdir (same isolation as optstr SOURCE=): escape FATAL before existence, missing tree FATAL, work tree that is the host CMAKE_SOURCE_DIR FATAL.
  Flush order is fixed: FETCH → SWITCH → RESET → PATCH (PATCH order is declaration order).
  Relative PATCH= is from CMAKE_CURRENT_SOURCE_DIR.
  Empty GIT / GIT={} is WARNING.
  Meta + any git op is FATAL.
  FETCH / RESET are inner flags.
  Post-install reset runs only when a PATCH was queued, and only inside that work tree (ROOT=).
• RENAME (flag, default ON).
  Post-install normalize of variant basenames.
  Libraries: oficio rename_library, worker component/rename/normalize_install_libraries.cmake.
  Executables: oficio rename_executable, worker normalize_install_executables.cmake.
  Headers mode never registers a rename oficio (stamps are not archives).
• WHOLE.
  Whole-archive link of produced static archives.
  Ignored (INFO) on headers and executable, including when that executable is a leaf of a WHOLE meta.
• STRIPRES (flag, default ON).
  After RENAME, strip *.res from static MSVC / clang-cl archives.
  Shared / headers / executable never strip.
• NOINSTALL + REPACK.
  Bare NOINSTALL builds without publishing to the shared prefix (artifacts stay under the component BUILDDIR; RENAME still runs there).
  NOINSTALL= and truthy NOINSTALL=ON|TRUE|1|YES enable with WARNING (write NOINSTALL, not NOINSTALL=…).
  Falsy values (OFF|FALSE|0|NO) are FATAL (omit the key to install).
  BUILDONLY is removed and FATAL (use NOINSTALL).
  Meta NOINSTALL is prevalent: finalize stamps every member.
  A unique backend is still used when detected; dual markers stay FATAL.
  buildmaster_meta(id title "REPACK") plus buildmaster_meta_add merges every produced static archive of the member leaves into one prefix archive named after the meta id.
  Wait edge is _install for every static member, including NOINSTALL.
  That target does not call cmake --install / meson install when NOINSTALL; it only runs oficios (rename, outputs, strip) on the BUILDDIR so REPACK sees the produced stem, not foo-static.lib.
  Shared members that install stay INTERFACE (WARNING: they are not folded into the pack).
  NOINSTALL + shared as a REPACK member is FATAL (the .so/.dll is not in the prefix and the builddir is not public).
  REPACK on buildmaster_component is valid for static only: first-level depend/link dests that are NOINSTALL static are the members; the publisher archive in the prefix is rewritten (POST_BUILD on <id>_install).
  REPACK + NOINSTALL on the same id is FATAL.
  REPACK + headers or executable on the same id is FATAL.
  Shared + REPACK on a component is WARNING + skip at finalize.
  Zero static members is FATAL.
  An executable dest of a REPACK publisher is skipped (INFO), not a member.
  An executable leaf of a REPACK meta is the same INFO skip and is not a merge INPUT.
  buildmaster_link to a NOINSTALL dest is FATAL (order-only: buildmaster_depend, or publish via a REPACK meta / component).
• Helper .pc (PC={…}).
  After install, write ${BUILDMASTER_INSTALL_LIBDIR}/pkgconfig/<Name>.pc for this prefix.
  FATAL if the path already exists.
  Not a portable package.
  NOINSTALL + enabled PC= is FATAL (no shared prefix).
  executable + enabled PC= is FATAL.
• Post-install oficios.
  Sealed GLOBAL BUILDMASTER_COMPONENT_<id>_INSTALL_OFICIOS is the ordered list (rename_library | rename_executable, outputs, strip_res, pc).
  _bm_install_rules_write emits only those files under scripts/install_rules/ and a rules aggregator with bare include().
  Templates have no if(@_BM_*_ENABLED@) feature flags.
  CMake and Meson share the same oficios.
  The stage wrapper is install_library.cmake.in → <id>_install_library.cmake (install_exec is gone).
  _BM_BUILDONLY remains the NOINSTALL token in wrappers and in the outputs oficio.
• Meta TOOLCHAIN inheritance.
  buildmaster_meta(… "TOOLCHAIN=<profile>") copies the profile onto members and onto empty dests.
  An explicit child TOOLCHAIN wins.
• Hooks.
  buildmaster_hook_component(id fn alias [CAPTURE …]) / buildmaster_hook_graph(fn alias [CAPTURE …]).
  fn must exist at registration.
  Alias is the only order key (ASCII ascending).
  CAPTURE snapshots by copy.
  A hook is not an edge and does not flip the component to deferred.
• Unified logging.
  _bm_log_message(<module> <level> "<text>" [<indent>]) is internal.
  Public buildmaster_message(<level> "<text>" [<indent>]) always uses module USER.
  WARNING and FATAL are never filtered.
  When BUILDMASTER_LOG_NOCOLOR is OFF, lines are painted: STATUS stays the default CMake color; WARNING yellow (message(NOTICE)); INFO green; DEBUG cyan; LOWLEVEL dim; FATAL red.
  ON leaves the text unpainted.
• BUILDMASTER_LOG_NOCOLOR.
  Truthy env or -D (1 / ON / TRUE / YES) stores ON and turns ANSI off; anything else is OFF (color on).
  Same pattern as BUILDMASTER_VERBOSE.
  Default OFF.
  Written into propagate_vars and the toolchain dump so nested -P scripts see the same switch.
• Silent env runner
  Replays nested [BuildMaster/…] lines live; the full child log is dumped on failure.
• Prefix search.
  Nested CMake gets BUILDMASTER_INSTALL_DIR prepended on CMAKE_PREFIX_PATH (runners export it; empty install dir is FATAL).
  Nested pkg-config still gets PKG_CONFIG_PATH first.
  find_package / *Config.cmake under the shared prefix resolve without per-leaf -DFOO_ROOT=.
• Toolchain translator.
  One pass per profile: drop foreign dialect and IPO tokens (-flto*, -ffat-lto-objects, -fno-fat-lto-objects, /GL, /LTCG, -fuse-ld=), rewrite -I/-L ↔ /I//LIBPATH:, then inject this profile’s linker flavor and IPO without writing -flto/-ffat-lto-objects back onto gcc/clang CMAKE_C{XX}_FLAGS.
  Those compile tokens live in BM_TC_IPO_COMPILE_OPTIONS so the leaf CMAKE_INTERPROCEDURAL_OPTIMIZATION module is the single dialect (-DCMAKE_<LANG>_COMPILE_OPTIONS_IPO=).
  LD still gets -flto or /LTCG.
  MSVC/clang-cl still write /GL or -flto on C/CXX.
  -fuse-ld= as before (see Fixed).
  Called from CMake/Meson stages before the env runner refresh.
  -fPIC stays on gcc/clang; it is dropped on msvc.
• On-demand tools.
  Bootstrap always initializes ninja.
  The archiver is not a tool: it is a field of the TOOLCHAIN= profile (CMAKE_AR / Meson [binaries] ar and ld).
  cmake, meson, git, and file initialize on first use: backend wrappers (cmake / meson), GIT={…} / FILES={…} on the optstr, or a pending FILES SOURCE after the tree is unpacked.
  Extra tools live under tools/extra/<id>/ (pkgconfig is the only extra in this release) and start only via REQUIRE_TOOL=<id> / REQUIRE_TOOL={id;id2} on buildmaster_component or buildmaster_meta.
  Empty REQUIRE_TOOL / REQUIRE_TOOL= / REQUIRE_TOOL={} is WARNING and ignored.
  An id that is not in BUILDMASTER_TOOLS_EXTRA_KNOWN (or whose directory is missing) is FATAL — BM never silently falls back to a same-named system binary.
  A second request is a no-op.
  PC={…} only writes a helper .pc; it does not demand pkgconfig.
  pkgconfig still prefers a working system pkg-config/pkgconf and builds the bundled tree only when that probe fails.
  BUILDMASTER_INITIALIZE_EXTRA_TOOLS is gone.
  Configure prints Setting up tools: <name> only when that tool actually starts.
  Compiler profiles follow the same rule: configure loads the parent profile inferred from CMAKE_C_COMPILER / CMAKE_CXX_COMPILER and writes only native_default.ini plus that profile’s Meson file.
  Any other name (gcc, clang, clang-cl, msvc) is demanded when a component or meta sets TOOLCHAIN= to it.
  Missing cc/cxx/ar/ld is FATAL on that id and names the parent profile plus CMAKE_C_COMPILER.
  A gcc job does not need clang, lld or llvm-ar on PATH.
  There is no REQUIRE_TOOL=gcc.
• Harness + consumer tests
  Recursive cmake/meson, helper .pc, meta-toolchain, LINKFLAGS (OPTIONS fold + no INTERFACE leak; meta ignore), hooks, late link, raw LINK=, duplicate edges, GIT={RESET;PATCH=…}, reset-then-patch, PC clobber (install FATAL), REPACK meta and component (including NOINSTALL members that emit *-static until _install rename), private-headers -I, FILES= unpack / SOURCE, FILES-on-meta FATAL, outline groups (CMake + Meson leaves), NOINSTALL (build without prefix publish), REQUIRE_TOOL=pkgconfig bundled path, BUILDONLY removed / NOINSTALL=OFF FATAL, mode executable (plain CMake/Meson, link a BM static, rename stem, NOINSTALL, REPACK publisher that ignores an executable dest, WHOLE meta + SHARED host that must not see the exe, exe-rescan static provider-before-consumer under IPO=fat), negatives exe-pc / exe-repack / exe-empty-produced, toolchain profile ar/ld text check (only the parent profile plus any TOOLCHAIN= actually used), translator dialect + /link order.
• Harness entry run_buildmaster_main.
  One target: smoke (install stages + artifacts) already depends on run_buildmaster_negative and run_buildmaster_consumer (consumer_nested); then a wiped sibling consumer_ci bindir.
  Local one-liner: rm -rf build/harness && cmake -S .github/tests/harness -B build/harness -G Ninja && cmake --build build/harness --target run_buildmaster_main.
• Configure report (BUILDMASTER_VERBOSE).
  After graph hooks, the primary bootstrap prints BuildMaster <version> Configuration: (module Report): parent toolchain paths/flags, then an alphabetical component table (ID / TYPE / LINK) with one-level NEEDED BY and explicit overrides only (CFLAGS, CXXFLAGS, FILES, LINKFLAGS, NOINSTALL).
  Groups are omitted.
  Row order is readability, not the graph walk.
  Nested bootstraps stay silent.
• IPO= on component and meta.
  Per-id LTO, independent of parent CMAKE_INTERPROCEDURAL_*.
  Omitted → inherit the parent (and leftover -flto / /GL tokens).
  IPO / IPO= / IPO=on → thin LTO (gcc/clang: CMAKE_INTERPROCEDURAL_OPTIMIZATION + compile-options -flto; clang-cl -flto on C/CXX; msvc /GL + /LTCG).
  IPO=off strips every IPO token even if the parent has IPO on.
  IPO=fat is thin plus -ffat-lto-objects on gcc/clang compile options only (BM_TC_IPO_COMPILE_OPTIONS / Meson c_args), never a second copy on CMAKE_C_FLAGS (that mixed -flto -ffat-lto-objects with CMake’s -flto=auto -fno-fat-lto-objects and the last token won).
  MSVC and clang-cl treat fat as on; no fat objects on LD.
  Darwin: AppleClang rejects -ffat-lto-objects, so fat is on (-flto only) and one STATUS notice is emitted per configure.
  Invalid values are FATAL.
  A meta with IPO= stamps members that omit the key (same destinations as TOOLCHAIN=); an explicit child IPO= wins and a second meta does not FATAL.
  CMake/Meson stages call _bm_tc_translate_component; Meson -Db_lto= follows the same mode.
  Harness: translator on/off/fat vs parent cache and BM_TC_IPO_COMPILE_OPTIONS; exe-rescan (provider before consumer + IPO=fat); negative ipo-bad (IPO=nope).

Changed

• Breaking — public API is buildmaster_* only.
  Ten commands (see public_functions.md): buildmaster_component, buildmaster_depend, buildmaster_link, buildmaster_meta, buildmaster_meta_add, buildmaster_group, buildmaster_group_add, buildmaster_hook_component, buildmaster_hook_graph, buildmaster_message.
  Internals are _bm_<craft>_* and are not a supported API.
  In particular:
  • create_cmake_component / create_meson_component / create_*_headers_component / create_component are gone. Use buildmaster_component.
  • component_link → buildmaster_link.
  • component_dependency → buildmaster_depend.
  • create_meta_component → buildmaster_meta.
  • meta_component_add → buildmaster_meta_add.
  • create_git_* / buildmaster_git_* → GIT={…} on the component.
  • file_download / file_download_cached / file_decompress → FILES={…} on the component. There is no public buildmaster_download* / buildmaster_decompress / buildmaster_prerequisite.
  • component_repack / buildmaster_repack are gone. Use buildmaster_meta(… "REPACK") + buildmaster_meta_add, or REPACK on a static buildmaster_component.
  • buildmaster_on_component_materialize → buildmaster_hook_component.
  • buildmaster_on_graph_finalized → buildmaster_hook_graph.
  • buildmaster_message public arity is <level> "<text>" [<indent>]. Module is always USER.
  • ensure_build_dir, sanitize_for_filename, import hints, toolchain profile/validate, archiver lookup, checksum and git marker are internal.
• Breaking — INDENT= is gone as a layout knob.
  The optstr key still parses so old trees configure, but it is WARNING + ignored (Use buildmaster_group / buildmaster_group_add for configure outline).
  Visual indent comes only from the group walk at configure time.
  Compile and install comments stay at indent 0.
• Breaking — no public build directory.
  buildmaster_component / _bm_backend_*_create do not take a builddir.
  The 2.0/2.1 arity heuristic is gone.
  Extra arguments are FATAL.
  _bm_path_builddir is gone.
  Callers that still pass a path get the arity FATAL (or CMake unknown-command if they called the deleted helper).
• Breaking — no buildmaster_repack.
  There is no public merge command, no OUTPUT= / INPUTS= parse arguments, no path tokens.
  Members of a REPACK meta are the inputs.
  The published stem is the meta id.
  Callers that still invoke buildmaster_repack get CMake’s unknown-command FATAL.
• Breaking — no generated fragment to include().
  No out-variable.
• Breaking — dependant factories are gone.
  Use buildmaster_component + buildmaster_depend (or buildmaster_link, which waits).
• Breaking — LINK_EXTRA is gone.
  Graph nodes: buildmaster_link.
  Raw system libs: LINK=.
• Breaking — LINKFLAGS is not INTERFACE.
  There is no target_link_options on <id>.
  Flags fold into that id’s nested OPTIONS only.
  A parent that links the component does not inherit -Wl,-Bsymbolic / /FORCE:MULTIPLE.
  Put flags on the id that actually builds, or on the final executable yourself.
  Meta LINKFLAGS is WARNING + ignored.
• Breaking — BUILDONLY is gone.
  Write NOINSTALL.
  The old key is FATAL.
  There is no NOINSTALL=OFF.
• Breaking — BUILDMASTER_DEBUG is gone.
• Breaking — options string.
  Flag keys may omit =.
  Known flags: RENAME, NOINSTALL, WHOLE, STRIPRES, PC, GIT, REPACK, FILES, REQUIRE_TOOL.
  BUILDONLY is accepted by the splitter only so the parser can FATAL.
  BACKEND= and SOURCE= require KEY=value.
  INDENT= is accepted only to warn.
  ; inside {…} is not a pair break.
  Unknown keys warn; extra positionals are fatal.
• Breaking — install wrapper.
  install_exec.cmake.in / <id>_install_exec.cmake are gone.
  Wrapper is install_library.cmake.in.
  Generated rules live under scripts/install_rules/.
  Worker normalize_install_outputs.cmake is normalize_install_libraries.cmake.
• Archiver is toolchain, not a tool.
  CMAKE_AR and Meson [binaries] ar / ld come from the component TOOLCHAIN= profile: msvc → lib.exe + link.exe; clang-cl → llvm-lib + lld-link; Linux clang → llvm-ar + ld.lld; Darwin clang → cctools ar + ld; Linux gcc → binutils ar + -fuse-ld=bfd; Darwin gcc → Homebrew gcc-N + cctools ar/ld (no CMAKE_LINKER_TYPE=BFD).
  A clang-cl parent does not force llvm-lib onto an msvc leaf or onto REPACK merge.
  Missing AR on a profile is FATAL (incomplete toolchain), not an optional tool miss.
• Stage COMMENT:
  configure stays CMake/Meson; compile and install use [BuildMaster/Ninja].
• Root CMakeLists.txt includes helpers before init_vars, so add_subdirectory(buildmaster) alone bootstraps a consumer.
• Root configure includes GNUInstallDirs.
• Post-install git reset + clean runs only after a PATCH, and only in the component work tree (GIT ROOT=), never in the host repo.
• Tools bootstrap is only ninja.
  The rest start on demand (REQUIRE_TOOL for extras).
  There is no BUILDMASTER_INITIALIZE_EXTRA_TOOLS.

Fixed

• Per-component TOOLCHAIN dump.
  Nested configures load a component toolchain file built from the parent registry: BUILDMASTER_INSTALL_*, template dirs (BUILDMASTER_TOOLS_CMAKE_SRCDIR, …) and ENV_* stay unified with the parent; only compilers/binutils are overridden.
  A toolchain override no longer bootstraps a second install tree under the component build dir.
  Incomplete snapshots (missing tool *_SRCDIR / ENV_*) no longer die with File /templates/configure.cmake.in does not exist when a nested project creates further components.
  Harness fixture tc-prefix locks the dump.
• Nested add_subdirectory(buildmaster) no longer corrupts the shared toolchain.cmake.
  When BUILDMASTER_CONFIGURED is already TRUE (host loaded the parent dump as CMAKE_TOOLCHAIN_FILE), the root CMakeLists.txt loads helpers, propagates vars, and returns — without toolchain_reset / module re-export / toolchain_write.
  Nested BM keeps BUILDMASTER_ROOT, BUILDMASTER_INSTALL_DIR and BUILDMASTER_CONFIGURED.
• Meson nested setups with system ld no longer pass -fuse-ld=/usr/bin/ld (or other absolute linker paths) into c_link_args / cpp_link_args.
• clang-cl + inherited MSVC LTCG flags.
  When the parent job uses clang-cl (or a stage selects TOOLCHAIN=clang-cl), stages strip /GL and /LTCG* from C/CXX and linker flags instead of forwarding them.
  The translator is the single place that puts profile IPO back (-flto or /GL+/LTCG).
• Meson on Windows (MSVC-like toolchains) does not inject /std:c11 into nested Meson c_args.
• Meson stages: SCCACHE_DIR path normalization no longer writes into CCACHE_DIR.
• Dependant configure targets under Ninja.
  Long configures no longer look hung; each dependant configure sets USES_TERMINAL and a clear COMMENT.
  On Windows + Ninja the redundant cmake -E echo that concatenated Configuring x twice is gone.
• Git operations never run in the host repository.
  A work tree equal to CMAKE_SOURCE_DIR, or a ROOT= / SOURCE= path that escapes the component srcdir, is FATAL before the tree is probed.
• Fragment GLOBAL BUILDMASTER_COMPONENT_<id>_NAMES / _FILES.
  Sealed after write_fragment so REPACK / meta merge see the produced archives.
• REPACK + NOINSTALL members wait <id>_install (oficios on the BUILDDIR), not <id>_build, so variant stems (*-static) are renamed before merge.
  Merge CMAKE_AR is the publisher TOOLCHAIN= archiver, not the parent CMAKE_AR.
• STRIPRES uses the component archiver.
  A msvc leaf built with lib.exe no longer lists/removes members with the parent’s llvm-lib (or the reverse) and warns no such file or directory for a name /LIST had just printed.
• Toolchain triples are mandatory.
  Linux gcc is binutils ar + -fuse-ld=bfd.
  Darwin gcc is Homebrew gcc-N + cctools ar/ld (no CMAKE_LINKER_TYPE=BFD, no -fuse-ld=bfd; Apple CMake rejects LINKER_TYPE 'BFD').
  Linux clang is llvm-ar + -fuse-ld=lld.
  Darwin clang is cctools ar + ld.
  clang-cl is llvm-lib + lld-link + -fuse-ld=lld on C/CXX and LD (Meson sanity ignores the flag after /link).
  msvc is lib.exe + link.exe.
  A missing tool of that triple is FATAL.
  Linux gcc/clang get -fuse-ld= on LD only (cc -c -Werror=unused-command-line-argument).
  Darwin gcc/clang get none (ld64).
• -fuse-ld= placement.
  clang-cl: on C/CXX and LD (Meson sanity is clang-cl <c_args> /link <c_link_args>; the driver ignores the flag after /link).
  Linux gcc / clang: LD only (cc -c -Werror=unused-command-line-argument + fuse-ld on C made dav1d report “Atomics not supported”).
  Darwin gcc / clang: no -fuse-ld (ld64).
  Harness checks all four.
• Darwin IPO=fat.
  -ffat-lto-objects is not passed on Apple (AppleClang rejects it; nested try_compile died).
  Fat becomes on.
  One STATUS per configure.