Merge "mkbootimg: Add '--boot_signature' and mark '--gki-*' as deprecated" am: 8bfa493d8e am: 3abe52d850 am: 14c7d4b133 am: d1e622c286

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

Change-Id: I30fbfa7829b56c06d4cecef9f268b35c3b73fc78