[automerger skipped] Add API to verify source stamp signature am: 92825ed1cc am: 278de80e10 am: 8b5a85f71e am: 8b64071dea -s ours

am skip reason: Change-Id I4675e9c50b0f4f9b0fd58aa9fbc15c9ee0313864 with SHA-1 92825ed1cc is in history

Original change: https://googleplex-android-review.googlesource.com/c/platform/tools/apksig/+/12237930

Change-Id: I1a96c096216b35b6c082de090e9209eb178afdd9