GCC 12.1 is out. Add support for it.
Deleted (upstreamed):
011-v12-configure-define-TARGET_LIBC_GNUSTACK-on-musl.patch
931-libffi-fix-MIPS-softfloat-build-issue.patch
Deleted (unneeded?)
970-macos_arm64-building-fix.patch
Other patches manually rebased due to C++ conversion and consequent file name
changing (.c to .cc).
Signed-off-by: Rui Salvaterra <rsalvaterra@gmail.com>
