Add support for post-submit-only ART gtests to `regen-test-files`. am: cda59b5354 am: 1e5a159438

Original change: https://android-review.googlesource.com/c/platform/art/+/2962582

Change-Id: Ied7bed965dc1dd38ca56227605c1b2fef80825fd
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>