androidmedia: also install java sources

As needed by our ndk-build integration
4 jobs for android-java in 6 minutes and 42 seconds (queued for 3 seconds)
Status Job ID Name Coverage
  Preparation
passed #58434
gst indent

00:00:31

passed #58433
manifest

00:00:18

 
  Build
passed #58435
build fedora x86_64

00:02:39

 
  Full Builds
passed #58436
build android arm64 api28

00:03:31