If we pass flags that make runs very slow, also the validity checks
might time out. Previously this wasn't checked and output was just
cut off.

This also tightens the timeout on validity checks as they are
expected to run very fast.

No-Try: true
Bug: chromium:1098646
Change-Id: Iea9a932be86e84040b72a2311aaa1d44100b3378
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2262915Reviewed-by: Maya Lekova <mslekova@chromium.org>
Reviewed-by: Tamer Tas <tmrts@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68510}