Merge "pixel3_mainline: Add changes to get pixel3_mainline building a boot.img (v3)" am: 679c9c12f8 am: 7e7b7b22b5 am: 477eb10c68 am: 21cd010ab8

Original change: https://android-review.googlesource.com/c/device/linaro/dragonboard/+/1354425

Change-Id: Ia41e33f2f75942deea10a106e49bb155cc30d2ac