Auto-generate restricted trace .gitignore. I'm going to add a non-ignored subdirectory so it behooves us to fix our blanket suppression. This will also allow users to clean up stale trace files. Bug: angleproject:4090 Bug: b/168049670 Change-Id: I5b0879eb3eebf3b352bb78e3b927203f9483c89f Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2426885 Commit-Queue: Jamie Madill <jmadill@chromium.org> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Cody Northrop <cnorthrop@google.com>