These are as similar to dscal_microk_skylakex-2.c as possible
for consistency.

Note that before this change SKYLAKEX+ uses generic C functions for
cscal/zscal via commit 2271c350 from #2610 (which is masked by
commit 086d87a30). However now #3799 disables FMAs (in turn enabled
by `-march=skylake-avx512`) in the plain C code which fixes excessive
LAPACK test failures more nicely.

If e.g. -march=haswell is set in CFLAGS, GCC generates FMAs by default, which
is inconsistent with the microkernels, none of which use FMAs. These
inconsistencies cause a few failures in the LAPACK testcases, where
eigenvalue results with/without eigenvectors are compared.

Moreover using FMAs for multiplication of complex numbers can give surprising
results, see 22aa81f for more information.

This uses the same syntax as used in 22aa81f for zarch (s390x).

Add pragma to disable the gcc tree-optimizer for some x86_64 S and Z kernels with gcc12 on OSX or Windows

Fix compilation for CooperLake on Windows/clang

actual initialization is via the _mm_cmpeq_ep18, which I've seen claimed to be the fastest way to set an xmm register to all 1s

Fix a few harmless compiler warnings