Enable use of AVX512 microkernels with NVIDIA HPC from version 22.3

Use SVE zgemm/cgemm on Arm(R) Neoverse(TM) V1 core

This patch removes the prefetches from cgemm/zgemm which improves the performance similar to sgemm/dgemm did in #3868, this means I'm happy to enable this on any applicable cores.

I also replicated the unrolling the copies from sgemm and dgemm.

Whilst disambiguating whilelt, I inadvertantly used the wrong datatype
for offsets, which can be negative. This rectifies that.

Use latest non-SVE kernels in ARMV8SVE

These are generally better and, in some cases, include threading which helps in the cores we're targeting here.

Restore zero-initialization of variables in generic ztrsm_utcopy

* Add AppleClang crossbuild to MacOS/arm64 DYNAMIC_ARCH

* add casts to disambiguate svwhilelt for clang

Sapphire Rapids sbgemm fix

This patch removes the warning messages related to unused variables in
sbgemm_kernel_power10.c.

Signed-off-by: Manjul Mohan <manjul@linux.vnet.ibm.com>

[WIP] Disable gcc's tree-vectorizer for x86_64 CGEMV

Use SVE kernel for SGEMM/DGEMM on Arm(R) Neoverse(TM) V1

Propagate SWITCH_RATIO to DYNAMIC_ARCH builds

This re-spins #3869 with some additional copy unrolling which helps maintain SYRK performance.

After #3868, the SVE kernels represent a pretty good boost.

This re-uses ARMV8SVE as a base and I'm going to incrementally move everything to use ARMV8SVE in additional patches (as well as fix up anything that's not already in ARMV8SVE).

Previously dynamic builds were either using the default SWITCH_RATIO
or one from the higher level architecture; this patch ensures the
dynamic builds can use this parameter as well.