[automerger skipped] repack_bootimg: Support using local files as repack source am: 5c9f40d974 -s ours

am skip reason: Merged-In I4afc676ebb169c909fce9c00189ef6f8cc46be7f with SHA-1 ac3ab67690 is already in history

Original change: https://googleplex-android-review.googlesource.com/c/platform/system/tools/mkbootimg/+/16331317

Change-Id: Ic9f445c4e73ec1d8130d31c3d48652dcecace73d