iOS uses 16kb memory pages. This change modifies OS::GetRandomMmapAddr()
to return a 16kb-aligned address on apple ARM64.

The mrs instruction is invalid on iOS. This change modifies
CacheLineSizes::CacheLineSizes() so that mrs is not executed.

Change-Id: I13fcc8498e715c03432c7a652ee723660f746069
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1701127Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#62730}