[heap] Don't assume that optimizing-compile-dispatcher exists

Bug: chromium:1215514, chromium:1211215
Change-Id: I6ebc1d4138d6bee66c3fd9a8369741b8df960807
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2933663


Commit-Queue: Georg Neis <neis@chromium.org>
Commit-Queue: Dominik Inführ <dinfuehr@chromium.org>
Auto-Submit: Georg Neis <neis@chromium.org>
Reviewed-by: Dominik Inführ <dinfuehr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#74929}