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
Local hints need to reduce (just like global hints do) so we expand
their definition to the lifted name before applying them.
We're identifying the global hints by knowing that the binder name is a
nested function name. This is a bit of hack, and it'd probably be better
to record that information in the binder instead, but that's a more
substantial change than I want to do right now.
