Compile dependencies prior to running test suite

[felixSchl]

Also see #12

We vendored the tests that come with the purescript compiler (for now). These tests are discovered, built, and executed in https://github.com/pure-c/pure-c/blob/c578687bff74370b92bdf95976b38c8adcc7b10d/test/Main.purs#L31-L59.

All tests use this makefile that is generated exactly once per pulp test:

https://github.com/pure-c/pure-c/blob/c578687bff74370b92bdf95976b38c8adcc7b10d/test/Main.purs#L61-L83

This means that all tests share the same build directory and thus can re-use shared build artifacts. Hence, the first build to run will take the longest, has it has to build a lot of the dependencies that are required. This will usually time out.

Instead, we should create a dummy target (or choose a test we consider infallible) that is built prior the actual tests running.