lang/gcc12-devel: Update to the 20210919 snapshot of GCC 12.0.0
files/patch-gcc-analyzer-bootstrap has been included upstream as has
an enhanced version of files/patch-libgfortran-bootstrap, alas we now
need files/patch-bootstrap-gcc-gcc.c as a temporary back port addressing
another bootstrap issue - "two steps forwards, one step back".
The internal compiler error on amd64 has been addressed, so unbreak
that architecture.