certify_bootimg: makes gki-info.txt optional am: 79627361ad am: 6236378e71 am: 8b855eb5f8 am: cade007f98 am: 4b5ad16a3a

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

Change-Id: I82058f4ecb1017fa5c5d809397c5476bc46c6304
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>