A recent change to remove empty tests runs cargo test --list. A few
crates produce build errors this way that they did not previously do.
This currently causes cargo2android.py to produce illegal Android.bp
files for these crates even though these should not be fatal errors.
We thus detect these errors and emit them as comments in the
Android.bp file, so developers can see them but the crate can still
compile.
Test: Run on crates with and without such errors.
Change-Id: I8664d3ca9a6b4c513ce0ef35821aa64d22949fc7
56b5f4be29