Merge "Remove deprecated BOARD_BUILD_SYSTEM_ROOT_IMAGE" am: 47ba5c4713 am: c9b1afa100 am: e499232eba

Original change: https://android-review.googlesource.com/c/device/generic/trusty/+/2175784

Change-Id: Ic5fc00ebbebc697f3fc051dc5b1063005ff190c1
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>