Merge "Disallow missing api source files for java_api_library module" am:...

Merge "Disallow missing api source files for java_api_library module" am: 0393174f am: 8faf87a3 am: 3a910094 am: 707c3a4b

Original change: https://android-review.googlesource.com/c/platform/build/soong/+/2593068



Change-Id: I25a0f0062808635616ed78118989f3855f37bdb7
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>