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

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

Change-Id: I6670c7acd654f9d8203bb247657b46cb34498028