Make sure to call `brew tests` only once with `--coverage` to avoid
expensive multiple runs and to prevent later runs from overwriting
previously sent results to Coveralls. (The previous setup overwrote the
results from a regular run with results from the `--generic` run.)
The `--no-compat` variant without any other options specified seemed to
be the most appropriate for a coverage report.
Closes#546.
Signed-off-by: Martin Afanasjew <martin@afanasjew.de>
5768e32ad2