gcc cleanups

[xnox]

• gcc: provide runtime libquadmath.so in a subpackage
  Currently libquadmath subpackage is empty, but should contain runtime
  libquadmath library, as used by boost and hdf5 on x86 only.

  aarch64 supports 128 precision without need for libquadmath runtime
  library.

# apk info -L libquadmath
libquadmath-13.3.0-r1 contains:
usr/lib64/libquadmath.so.0
usr/lib64/libquadmath.so.0.0.0
var/lib/db/sbom/libquadmath-13.3.0-r1.spdx.json

• gcc: stop building objc
  objc compiler typically requires gnustep libraries to be usable, which
  Wolfi does not package. Unused by any of the packages in Wolfi and not
  shipped in any Chainguard Images.

• gcc: set full pkgversion like clang

# gcc --version
gcc (Wolfi 13.3.0-r1) 13.3.0
Copyright (C) 2023 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

• gcc: set with-arch & with-mtune
  Use current settings of march from build-flags. Bump mtune to
  current/latest generation of silicon available in the public clouds.

# gcc -Q --help=target | grep -e march= -e mtune= | head -n2
  -march=                     		x86-64-v2
  -mtune=                     		sapphirerapids

# gcc -Q --help=target | grep -e march= -e mtune=
  -march=                     		armv8-a+crc+crypto
  -mtune=                     		neoverse-v2

• gcc: (build) avoid linking compilers at the same time

• gcc: bump epoch

resolved

[pnasrat]

LGTM

[smoser]

thank you.