If multiple recompilations are triggered at the same time, we cannot
contribute to compilation, because this would bump the number of workers
above the maximum expected concurrency.

This is a quick fix, a better (but more involved) fix would be to make
the number of queues grow dynamically.

R=thibaudm@chromium.org

Bug: chromium:1123471

Cq-Include-Trybots: luci.v8.try:v8_linux64_tsan_rel_ng
Cq-Include-Trybots: luci.v8.try:v8_linux64_tsan_isolates_rel_ng
Change-Id: I30e4b2a057098ad7267ae942e5845b0cefe60e0b
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2387561Reviewed-by: Thibaud Michaud <thibaudm@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#69639}