Support sparse images in map_file_generator am: 8bd5c4ccde am: bc9acdf3c0

Original change: https://android-review.googlesource.com/c/platform/system/update_engine/+/2620452

Change-Id: Ib1a76c77708dfd10fdc4c4f88c97d19de0b7ba40
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>