improve error handling for SourceRootDirs am: 48020c8daa am: d5d574c65f am: d8de876ee5 am: 957dfc44cd

Original change: https://android-review.googlesource.com/c/platform/build/blueprint/+/2515504

Change-Id: I1400f975782b6f391e3ac5d6a26c4cafc24c5693
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>