This helps reduce the number of false positives encountered by
the dead variable analysis in gcmole.

TBR=jgruber@chromium.org, verwaest@chromium.org, yangguo@chromium.org

Bug: v8:9810
Change-Id: I1a34ccaab340e6abc37832b4ce1a0cabc56fa438
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1917146
Commit-Queue: Maya Lekova <mslekova@chromium.org>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#64981}