meson: use subproject for internal libfdt

Recent dtc/libfdt can use either Make or meson as the build system.
By using a subproject, our own meson.build can remove the hard
coded list of source files.

This is also the first step towards managing downloads with .wrap
files instead of submodule.

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

.gitmodules

@@ -13,8 +13,8 @@
 [submodule "roms/qemu-palcode"]
 	path = roms/qemu-palcode
 	url = https://gitlab.com/qemu-project/qemu-palcode.git
-[submodule "dtc"]
-	path = dtc
+[submodule "subprojects/dtc"]
+	path = subprojects/dtc
 	url = https://gitlab.com/qemu-project/dtc.git
 [submodule "roms/u-boot"]
 	path = roms/u-boot

configure

@@ -1187,7 +1187,7 @@ fi
 case "$fdt" in
   auto | enabled | internal)
     # Simpler to always update submodule, even if not needed.
-    git_submodules="${git_submodules} dtc"
+    git_submodules="${git_submodules} subprojects/dtc"
     ;;
 esac
 

meson.build

@@ -3088,26 +3088,10 @@ if fdt_required.length() > 0 or fdt_opt == 'enabled'
       error('libfdt source not found - please pull git submodule')
     endif
 
-    fdt_files = files(
-      'dtc/libfdt/fdt.c',
-      'dtc/libfdt/fdt_ro.c',
-      'dtc/libfdt/fdt_wip.c',
-      'dtc/libfdt/fdt_sw.c',
-      'dtc/libfdt/fdt_rw.c',
-      'dtc/libfdt/fdt_strerror.c',
-      'dtc/libfdt/fdt_empty_tree.c',
-      'dtc/libfdt/fdt_addresses.c',
-      'dtc/libfdt/fdt_overlay.c',
-      'dtc/libfdt/fdt_check.c',
-    )
-
-    fdt_inc = include_directories('dtc/libfdt')
-    libfdt = static_library('fdt',
-                            build_by_default: false,
-                            sources: fdt_files,
-                            include_directories: fdt_inc)
-    fdt = declare_dependency(link_with: libfdt,
-                             include_directories: fdt_inc)
+    libfdt_proj = subproject('dtc', required: true,
+                             default_options: ['tools=false',  'yaml=disabled',
+                                               'python=disabled', 'default_library=static'])
+    fdt = libfdt_proj.get_variable('libfdt_dep')
   endif
 else
   fdt_opt = 'disabled'

scripts/archive-source.sh

@@ -26,7 +26,7 @@ sub_file="${sub_tdir}/submodule.tar"
 # independent of what the developer currently has initialized
 # in their checkout, because the build environment is completely
 # different to the host OS.
-submodules="dtc ui/keycodemapdb"
+submodules="subprojects/dtc ui/keycodemapdb"
 submodules="$submodules tests/fp/berkeley-softfloat-3 tests/fp/berkeley-testfloat-3"
 sub_deinit=""