certify_bootimg: support --extra_footer_args am: f754a7c3b8 am: a86f4ddbf6 am: 12bcad6963 am: ee599a6116

Original change: https://android-review.googlesource.com/c/platform/system/tools/mkbootimg/+/2104149

Change-Id: I4c0bce34a5e2b8c2a6db9feb04c9698ee5248de9
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>