certify_bootimg: makes gki-info.txt optional am: 79627361ad am: 6236378e71 am: 8b855eb5f8 am: cade007f98 am: 0674b7ccb3

Original change: https://android-review.googlesource.com/c/platform/system/tools/mkbootimg/+/2051402

Change-Id: Ie2431fc4d73f21a953b04c3dfd571ecbca7b628c
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>