Merge "Turns on building vbmeta.img when merging if avb_enable=true." am:...

Merge "Turns on building vbmeta.img when merging if avb_enable=true." am: adcf94d5 am: b8939490 am: 1d64807a am: bbebe256

Original change: https://android-review.googlesource.com/c/platform/build/+/1506497

Change-Id: I0cd3e9e57b5989b5822c225064320f0e6c42ac5c