While the discussion about how to refactor test framework is not
finished (#1654), make this change: move `rm -rf build` in the
beginning of the test. For these reasons:
* it is useful to inspect the contents of the `build` directory
especially after the test failure
* if build crashes mid-test (e.g. process killed), next run should
not be affected by the `build` directory from the previous run
Because it relies on the source file that I've just fixed for the
linter. I think I've now spent more time pleasing the linter than fixing
the actual bug...
We need to fully evaluate, not just the public export names, otherwise
we don't pattern match properly and potentially generate catch all
patterns we don't mean.
Fixes#1537
