Respect SYSTEM_EXT_ROOT in odrefresh am: 0a964610eb am: 79ba38e312 am: 9781b7bf27

Original change: https://android-review.googlesource.com/c/platform/art/+/2225897

Change-Id: Ieb2b350be6b7f58b0725d65f6b70c6712311086c
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>