In this commit, we adapt the Makefile that was being used for the
btcutil project to work for btcd as well. The Makefile is pretty simple,
and is just a series of templated commands. Overtime, we can pull in
some of the `lnd` additions as well, which we use to handle our
reproducible build and verification system.
This modifies the goclean.sh script to run tests with the
race detector enabled. It also enables code coverage, and
uploads the results to coveralls.io.
Running tests with -race and -cover flags was disabled in
6487ba1 and 6788df7 respectively, due to some limits on
time/goroutines being hit on Travis CI. Since we have
migrated to GitHub Actions, it is desirable to bring them
back.
