Merge "Add support for missing public / private key files for apexes." am:...

Merge "Add support for missing public / private key files for apexes." am: babb1337 am: d2344eea am: 595514bf

Original change: https://android-review.googlesource.com/c/platform/build/soong/+/2586953



Change-Id: I2b86ccf5719a5a851b5315e449d4a5c0b78d6be6
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>