Due to the transition to the jobs API, WebAssembly compilation was using
background threads, even when --single-threaded and therefore
--wasm-num-compilation-tasks=0 was used. With this CL, the compilation
job is started with a maximum concurrency of 0 when
--wasm-num-compilation-tasks=0. To ensure compilation progress in
asynchronous compilation, the main thread waits for baseline compilation
to finish right after initializing all compilation units, and thereby
participates in the compilation.

R=clemensb@chromium.org

Bug: v8:11279
Change-Id: I85f93f82c00cdbd6afd46110599089a052101a00
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2599546Reviewed-by: Clemens Backes <clemensb@chromium.org>
Commit-Queue: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#71944}