If source positions are not required when a background compilation task
starts, but then something like profiling is started before the task
finalizes, then logging of the compilation task will crash due to a
missing source position table.

This ensures source positions are collected if source positions are
required during finalization.

R=rmcilroy@chromium.org

Bug: chromium:1022749
Change-Id: Ie83c3d88131a1c1f434274ea9ee52895c6753b49
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1942611
Commit-Queue: Dan Elphick <delphick@chromium.org>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#65251}