Merge "build_image: Query the actual image size after invoking the final...

Merge "build_image: Query the actual image size after invoking the final mkfs." am: 0096a750 am: 965ca0d9 am: f301d211

Original change: https://android-review.googlesource.com/c/platform/build/+/1889816

Change-Id: I755ca7259857d6d5a0ed5fd6d07472b18812d9b7