Fixes the use of v8_enable_fast_mksnapshot on platforms that
aren't ia32 or x64. This was introduced by
https://chromium-review.googlesource.com/c/v8/v8/+/3863281

Change-Id: I0d18c2d16dae4937baa40ee336d8c246a8b77889
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3867408Reviewed-by: Igor Sheludko <ishell@chromium.org>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Commit-Queue: George Wort <george.wort@arm.com>
Cr-Commit-Position: refs/heads/main@{#82945}