In CodeStubAssembler::TryToIntptr(), code inside an Is64() block is
compiled on 32-bit, but |kMaxSafeIntegerUint64| cannot fit in an
intptr_t. To avoid this error, guard the Is64() block with
V8_TARGET_ARCH_64_BIT.

Change-Id: I5d82e4f649172e6054a767cc263a42bc02f89e58
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1960906Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#65420}