Fix builds on BSD
Fix builds on BSD

Fix the build on BSD by setting PROCESSOR_IS_X86 when CMAKE_SYSTEM_PROCESSOR
matches amd64.

Signed-off-by: Steven Kreuzer <a11fca3a48cb993a0c6d1439f6bdefa332b83412@FreeBSD.org>

google/cpu_features,google/cpu_features,google/cpu_features