Without this, the mac/arm64 linker complains:

ld: warning: arm64 function not 4-byte aligned:
    _PushAllRegistersAndIterateStack from obj/v8/v8_cppgc_shared/push_registers_asm.o
ld: fatal warning(s) induced error (-fatal_warnings)

It's probably a good idea to use the same alignment on all platforms, so
do this everywhere, not just on mac.

Bug: chromium:1099892
Change-Id: I15ca7bac04e1a1a1de09ecdfeaddd9e788051755
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2283908
Auto-Submit: Nico Weber <thakis@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68701}