Also add the ability to skip tests only when --optimize-for-size is passed.

TBR=sergiyb@chromium.org

Bug: v8:7819
Change-Id: I1dcc26ea8664d014b6c50f0d636c13bf21e26ff2
Reviewed-on: https://chromium-review.googlesource.com/c/1328945Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#57396}