Add AOCL_ENABLE_INSTRUCTIONS environment variable as an alternative
to BLIS_ARCH_TYPE. The details are:
1. AOCL_ENABLE_INSTRUCTIONS and BLIS_ARCH_TYPE env vars are both
supported, with BLIS_ARCH_TYPE taking precedence if both are set.
2. Values of "avx2" and "avx512" are aliases for "zen3" and "zen4"
code paths respectively in AMD focused builds, or for "skx" and
"haswell" respectively in Intel focused builds. These names are
not case-sensitive.
3. BLIS_ARCH_TYPE specifies the code path to use. If this is
unsupported, e.g. zen4 code path on a Milan or earlier system,
that code path is still executed, likely resulting in an illegal
instruction error.
4. By contrast, AOCL_ENABLE_INSTRUCTIONS will check ISA support on
the system (for AVX2 and AVX512), and try a "lower" ISA option if
the desired one is not supported, i.e. AVX512->AVX2, AVX2->generic.
5. Appropriate messages are printed if BLIS_ARCH_DEBUG=1 is set.
AMD-Internal: [CPUPL-4105]
Change-Id: Ia941b41d4b7d11f5589d7c5e16f607618baed315
248dc2af9a