Patch GCC 4.7.4 for native musl support

Backport upstream patches to enable native musl toolchain support in
GCC. Only the changes required for i386 were taken, excluding
changes for libgo and libfortran.

These patches enable binaries built using gcc and g++ to automatically
use musl's dynamic linker as their interpreter when present during the
build.

sysc/gcc-4.7.4/patches/0004-libstdc-gthr-workaround-for-musl.patch

@@ -0,0 +1,41 @@
+SPDX-FileCopyrightText: 2022 Dor Askayo <dor.askayo@gmail.com>
+SPDX-FileCopyrightText: 2015 Szabolcs Nagy <szabolcs.nagy@arm.com>
+
+SPDX-License-Identifier: GPL-2.0-or-later
+
+Backported from upstream commit 85da5c3024f731e719c4093314da8edcd1056527
+
+libstdc++ gthr workaround for musl
+
+[libstdc++-v3/]
+2015-04-22  Szabolcs Nagy  <szabolcs.nagy@arm.com>
+
+	* config/os/generic/os_defines.h (_GLIBCXX_GTHREAD_USE_WEAK): Define.
+	* configure.host (os_include_dir): Set to "os/generic" for linux-musl*.
+
+From-SVN: r222329
+
+--- libstdc++-v3/config/os/generic/os_defines.h
++++ libstdc++-v3/config/os/generic/os_defines.h
+@@ -33,4 +33,9 @@
+ // System-specific #define, typedefs, corrections, etc, go here.  This
+ // file will come before all others.
+ 
++// Disable the weak reference logic in gthr.h for os/generic because it
++// is broken on every platform unless there is implementation specific
++// workaround in gthr-posix.h and at link-time for static linking.
++#define _GLIBCXX_GTHREAD_USE_WEAK 0
++
+ #endif
+--- libstdc++-v3/configure.host
++++ libstdc++-v3/configure.host
+@@ -242,6 +242,9 @@ case "${host_os}" in
+   freebsd*)
+     os_include_dir="os/bsd/freebsd"
+     ;;
++  linux-musl*)
++    os_include_dir="os/generic"
++    ;;
+   gnu* | linux* | kfreebsd*-gnu | knetbsd*-gnu)
+     if [ "$uclibc" = "yes" ]; then
+       os_include_dir="os/uclibc"