This is a major contributor to compilation (call path is
ExecuteCompilationUnits -> TopTierFinished -> SerializeNativeModule).
On Earth, it's ~200ms on my machine. Hence make this pause visible in
traces.

R=ahaas@chromium.org

Change-Id: I26ff97d531647fa7038f14325e8ab8ae3dff24e5
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2520909Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#71046}