Merge "mkbootimg: Add '--boot_signature' and mark '--gki-*' as deprecated" am: 8bfa493d8e am: 3abe52d850

Original change: https://android-review.googlesource.com/c/platform/system/tools/mkbootimg/+/1933195

Change-Id: I6ec9f5a3fd3133a442b231e6ed34208168f99a9a