GitLab

Some buildbots are executing `ninja all` and fuzz targets should not
be attempted to be built there unless certain GN flags are enabled.

Bug: 999096
Change-Id: I11addbe7ab00a5ef8c57559bd84a1ec4b287f212
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1775756
Commit-Queue: Max Moroz <mmoroz@chromium.org>
Reviewed-by: Matt Mueller <mattm@chromium.org>
Reviewed-by: Robert Sesek <rsesek@chromium.org>
Cr-Commit-Position: refs/heads/master@{#691764}