They check for AVX and uses the AVX instruction if available. This is a
follow-up CL to https://crrev.com/c/v8/v8/+/2912778

Change-Id: Ib53f06f03ac1067366b76b9193d8db98c394ce50
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2919853
Auto-Submit: Santiago Aboy Solanes <solanes@chromium.org>
Reviewed-by: Zhi An Ng <zhin@chromium.org>
Commit-Queue: Zhi An Ng <zhin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#74795}