sh_binary: Implement OutputFileProducer for sh_test

When added as a data dependency, the output of sh_test does not get
included.  It needs to define OutputFiles in order to implement the
OutputFileProducer interface.

Bug: 293944582
Test: N/A
Change-Id: Ic27741ed584523f5e1efd7caa8b872fe50cce381
Signed-off-by: Edward Liaw <edliaw@google.com>