Add an option to "demultilib"

It turns out buildroot does not currently accept a toolchain where a dynamic
linker does not reside in the multi-os-directory. Unfortunately this is
how glibc installs itself on AArch64 without any extra tricks.

So, provide an option to force everything into /lib or /usr/lib; patch to
buildroot will be worked on separately.

Signed-off-by: Alexey Neyman <stilor@att.net>

config/target.in

@@ -51,6 +51,29 @@ config MULTILIB
       NOTE: The multilib feature in crosstool-NG is not well-tested.
             Use at your own risk, and report success and/or failure.
 
+config DEMULTILIB
+    bool "Attempt to combine libraries into a single directory"
+    default y if !MULTILIB
+    depends on !MULTILIB || EXPERIMENTAL
+    help
+      Normally, Crosstool-NG installs the libraries into the directories
+      as the configure for these libraries determines appropriate. For
+      example, for AArch64 glibc wants to install the libraries into
+      /lib64 but the default dynamic linker path is /lib/ld-linux-aarch64.so.1
+      (which is installed as a symlink to ../lib64/ld-VER.so).
+
+      However, not all consumers of the toolchain can handle the libraries
+      residing in multiple directories. To appease them, crosstool-NG can
+      attempt to combine the libraries back into a single /lib directory and
+      create all other directories as symlinks to /lib. This requires all
+      the library names to be unique within each sysroot.
+
+      Note that GCC may also use separate sysroots for different multilibs.
+      Hence it may make sense to enable this option even for multilib toolchains.
+      However, separate roots are rare (any other architecture aside from
+      SuperH using them?) and hence not well tested in crosstool-NG; therefore,
+      this option is experimental when MULTILIB is enabled.
+
 #--------------------------------------
 config ARCH_SUPPORTS_BOTH_MMU
     bool

scripts/build/cc/100-gcc.sh

@@ -129,6 +129,40 @@ cc_gcc_classify_opt() {
     echo "unknown"
 }
 
+evaluate_multilib_cflags()
+{
+    local multi_dir multi_os_dir multi_os_dir_gcc multi_root multi_flags multi_index multi_count
+    local mdir mdir_os dirtop
+    local f
+
+    for arg in "$@"; do
+        eval "${arg// /\\ }"
+    done
+
+    mdir="lib/${multi_dir}"
+    mdir_os="lib/${multi_os_dir_gcc}"
+    CT_SanitizeVarDir mdir mdir_os
+    CT_DoLog EXTRA "   '${multi_flags}' --> ${mdir} (gcc)   ${mdir_os} (os)"
+    for f in ${multi_flags}; do
+        eval ml_`cc_gcc_classify_opt ${f}`=seen
+    done
+    if [ "${CT_DEMULTILIB}" = "y" ]; then
+        case "${mdir_os}" in
+            lib/*)
+                ;;
+            *)
+                dirtop="${mdir_os%%/*}"
+                if [ ! -e "${multi_root}/${mdir_os}" ]; then
+                    CT_DoExecLog ALL ln -sfv lib "${multi_root}/${mdir_os}"
+                fi
+                if [ ! -e "${multi_root}/usr/${mdir_os}" ]; then
+                    CT_DoExecLog ALL ln -sfv lib "${multi_root}/usr/${mdir_os}"
+                fi
+                ;;
+        esac
+    fi
+}
+
 #------------------------------------------------------------------------------
 # This function lists the multilibs configured in the compiler (even if multilib
 # is disabled - so that it lists the default GCC/OS directory, which may differ
@@ -151,9 +185,11 @@ cc_gcc_classify_opt() {
 # work, but 'gcc -mabi=32 -mabi=n32' produces an internal error in ld. Thus we do
 # not supply target's CFLAGS in multilib builds - and after compiling pass-1 gcc,
 # attempt to determine which CFLAGS need to be filtered out.
+#
+# 3. If "demultilibing" is in effect, create top-level directories for any
+# multilibs not in lib/ as symlinks to lib.
 cc_gcc_multilib_housekeeping() {
     local cc host
-    local flags osdir dir multilibs i f
     local multilib_defaults
     local suffix sysroot base lnk
     local ml_arch ml_abi ml_cpu ml_tune ml_fpu ml_float ml_endian ml_mode ml_unknown ml
@@ -175,25 +211,7 @@ cc_gcc_multilib_housekeeping() {
     multilib_defaults=( $( cc_gcc_get_spec multilib_defaults "${cc}" | \
         sed 's/\(^\|[[:space:]]\+\)\([^[:space:]]\)/ -\2/g' ) )
     CT_DoLog EXTRA "gcc default flags: '${multilib_defaults}'"
-
-    multilibs=( $( "${cc}" -print-multi-lib ) )
-    if [ ${#multilibs[@]} -ne 0 ]; then
-        CT_DoLog EXTRA "gcc configured with these multilibs (including the default):"
-        for i in "${multilibs[@]}"; do
-            dir="lib/${i%%;*}"
-            flags="${i#*;}"
-            flags=${flags//@/ -}
-            flags=$( echo ${flags} )
-            osdir="lib/"$( "${cc}" -print-multi-os-directory ${flags} )
-            CT_SanitizeVarDir dir osdir
-            CT_DoLog EXTRA "   '${flags}' --> ${dir} (gcc)   ${osdir} (os)"
-            for f in ${flags}; do
-                eval ml_`cc_gcc_classify_opt ${f}`=seen
-            done
-        done
-    else
-        CT_DoLog WARN "no multilib configuration: GCC unusable?"
-    fi
+    CT_IterateMultilibs evaluate_multilib_cflags evaluate_cflags
 
     # Filtering out some of the options provided in CT-NG config. Then *prepend*
     # them to CT_TARGET_CFLAGS, like scripts/crosstool-NG.sh does. Zero out