The test runner is stuck on start-up otherwise.

TBR=sergiyb@chromium.org
NOTRY=true

Bug: v8:8552
Change-Id: Ief2632ce168f83ae33bc9ae1f7edee152505cae9
Reviewed-on: https://chromium-review.googlesource.com/c/1437276Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#59107}