This test attempted to call mprotect to switch memory permissions,
which returns an error on MacOS on arm64. The workaround is simple:
don't call mprotect, rely on MacOS-specific permission switching.

See also https://chromium-review.googlesource.com/c/v8/v8/+/2679688
for a related fix in non-test code.

Drive-by: fix host arch detection in gm.py when building on M1 Macs.

Bug: v8:11657
Change-Id: I9b59ee8f2279e28f7561ac071df27508211741f3
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2831877Reviewed-by: Clemens Backes <clemensb@chromium.org>
Commit-Queue: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#74030}