Do not generate empty Rust tests.

cargo2android.py currently builds whatever cargo does, which includes
empty tests.  We can filter those out by parsing the output of "cargo
test" and looking for things with no tests.

Fixes: 159039990
Test: Run on a crate with empty integration tests, one with empty unit
tests, and one with no empty tests.

Change-Id: If8b1126d82ce6c2851b90de738ea24b129b81feb
1 file changed