update_engine: xor writer size_t am: ae222aa0f8 am: cdee8a414c

Original change: https://android-review.googlesource.com/c/platform/system/update_engine/+/3343486

Change-Id: I5f8dcd191a6f2b1b6ab36e1332d8c87b42dd3a6d
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>