Merge "STT: add ninja "explain" to see the reason of build triggers" am: b14b8a6334 am: fdccaeea39 am: 4ad9dae6d9 am: 5c5ac03272 am: 1a5416fd60 am: 8b9267ea56

Original change: https://android-review.googlesource.com/c/platform/development/+/2640397

Change-Id: Ic48432ae32ff49bf1385abc860455619b0921014
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>