Two of them were in comments; updated them to V8_OS_MACOSX.

Two of them were incorrectly in #if statements. Updated them to
V8_OS_MACOSX.

Bug: chromium:823915, chromium:1105907
Change-Id: Ibfc0f8936dbc8cbf3b05a674e882bbc480d0b4c4
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2331736Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Avi Drissman <avi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#69178}