package/gcc: add patch to fix glibc header conflict

This commit backports the patch "fixinc: don't "fix" machine names in
__has_include(...)" from upstream GCC, which is needed to resolve a
header conflict between glibc headers and kernel headers, which has
appeared since we bumped glibc to version 2.36 in commit
80c8c15c.

The problem comes from the "fixinc" logic used by gcc to fixup some
headers files, generated inside an include-fixed/ folder. This logic
ended up replacing "linux/mount.h" by "__linux__/mount.h" in
__has_include() invocation, like this:

 #ifdef __has_include
 # if __has_include ("__linux__/mount.h")
 #  include "linux/mount.h"
 # endif
 #endif

in
build/host-gcc-final-11.3.0/build/gcc/include-fixed/sys/mount.h. With
this fix in place, this "include-fixed" header is no longer generated,
avoiding the problem.

This issue was visible in two different ways in glibc configurations:

 - As a build failure during the gcc build itself, for architectures
   that...