Merge "Properly track where a build flag is declared" into main am: 5078551e

Original change: https://android-review.googlesource.com/c/platform/build/soong/+/3132914



Change-Id: I661af7b1cdcabe87b0d71b0113cd2087823ccc10
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>