fix empty test detection for cargo workspaces

The main src file path is relative to a crate's root dir. Nearly all the
crates in a workspace have the same path for their tests (src/lib.rs).
Thankfully the package name is included in the log, so we can use it to
differentiate.

Bug: 242733327
Test: run on crosvm and see some empty tests get trimmed from Android.bp files
Change-Id: I0ed17a05bfcccb78557ac10a818bf8640eefea7d
1 file changed