This change will allow the AVX version of non-temporal memcpy to be compiled
even if the compiler isn't run with AVX support. This allows runtime dispatch
to select the AVX implementation for CPUs that are known to be compatible with
AVX instructions.

PiperOrigin-RevId: 619594422
Change-Id: Ia7d92404ef8d10d152030b29b71948ed954f28f5