Merge "Allow BOARD_BUILD_SYSTEM_ROOT_IMAGE override by command line flag." am: c32d31d4fa am: 9e108ef038

Original change: https://android-review.googlesource.com/c/device/generic/common/+/2039603

Change-Id: If209f5e5821393769b1b6f1d12b1aa4599d33abc
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>