The march=cooperlake and march=sapphirerapids flags were never getting
added when building with Clang targetting those architectures. Instead
it was falling back to the skylake AVX512 implementation.

Clang added support for these two architectures in Clang 9 and Clang 12,
so introduce new checks for those versions to enable the appropriate
march flag, and fallback to skylake otherwise.

for #3139

Enable new build target platform -- COOPERLAKE. This target platform
supports all the SKYLAKEX supported ISAs + avx512bf16. So all the
SKYLAKEX specific kernels/drivers and related code are now extended
to be also active on COOPERLAKE. Besides, new BF16 related kernels
are active under this target.

original issue was #1708, I see now that the same problem affects gfortran compilation. The underlying issue is said to be fixed (but not yet released) on all branches of gcc as of a few days ago but it will certainly take time to reach mingw/msys.

fixes compile failure with pgi 18.10 as reported on OpenBLAS-users

to leverage improvements from PR#1921

fixes #1708

Signed-off-by: Timothy Gu <timothygu99@gmail.com>