Make exclude_unwind_tables only dependent on is_official_build

This is an optimization setting, not a branding setting, so
it shouldn't look at is_chrome_branded.

No behavior change for builds covered by our bots, but it
might enable the setting for out-of-tree forks.

Bug: none
Change-Id: I8444cc4d01bf654ae2c6d46662fa6a142b08c0de
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1593404
Auto-Submit: Nico Weber <thakis@chromium.org>
Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Commit-Queue: Nico Weber <thakis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#656113}
1 file changed