This fixes an ODR violation: the macro V8_TARGET_ARCH_ARM64 was only
visible when building V8, but not outside it. The CL implements a quick
fix that relies on compiler-based macros (__aarch64__). The proper fix
would be to make these target macros be part of the public config.

Bug: chromium:1336222
Change-Id: I46ba6c1a3cd1ac4fcd3aced60ee112e6098eba6c
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3705540
Commit-Queue: Anton Bikineev <bikineev@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Auto-Submit: Anton Bikineev <bikineev@chromium.org>
Cr-Commit-Position: refs/heads/main@{#81162}