MDEV-22641 in commit dec3f8ca
refactored a SIMD implementation of CRC-32 for the ISO 3309 polynomial
that uses the IA-32/AMD64 carry-less multiplication (pclmul)
instructions. The code was previously only available in Mariabackup;
it was changed to be a general replacement of the zlib crc32().

There exist AMD64 systems where CMAKE_SYSTEM_PROCESSOR matches
the pattern i[36]86 but not x86_64 or amd64. This would cause a
link failure, because mysys/checksum.c would basically assume that
the compiler support for instruction is always available on GCC-compatible
compilers on AMD64.

Furthermore, we were unnecessarily disabling the SIMD acceleration
for 32-bit executables.

Note: Until MDEV-22749 has been implemented, the PCLMUL instruction
will not be used on Microsoft Windows.

Closes: #1660