It is becoming difficult to continue supporting the compiler dispatcher
and background compile task unittests alongside the off-thread
finalization work, so disable those tests when that flag is enabled.

Bug: chromium:1011762
Change-Id: Iba9aaa29b08723afb90edc127609fef1d63ceed5
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2539908
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Auto-Submit: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#71211}