Add lz4diff CLI util am: 35cff4f58e am: d8d8e8b0a6 am: b3c1f582e4

Original change: https://android-review.googlesource.com/c/platform/system/update_engine/+/1915661

Change-Id: I55b6f4f8d83ab2ee4f02757af620658a382ea9bf