asm-to-wasm doesn't support off-thread finalization, so disable it if an
asm compilation job is successfully executed. Note that in the future,
we could instead have a hybrid off-thread and main-thread finalization
for mixed JS and asm.js scripts, but for now that's probably
unncecessary.

Bug: chromium:1011762
Change-Id: I52c8f31fa13790e03ccf3196dbef471bca387bc5
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2110017
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#67364}