Update comp-builder to run tests directly

[ruhatch]

This PR aims to get around several issues we've been experiencing running test suites with cabal. Instead of using $SETUP_HS to run the test executables in checkPhase, we run them directly.

To allow for test wrappers, such as wine, required on some systems, we add a testWrapper option to the package options. This will then be set in iohk-nix/mingw_w64.nix instead of setupTestFlags to get the same wine wrapper in place.

[angerman]

Lgtm

[michaelpj]

This is what haskell/cabal#5995 is for, right? I guess we don't have a cabal release with that in yet. It would be good to have a comment that we should remove this one we can use that cabal option.

[ruhatch]

@michaelpj we were using that flag before, but cabal was being problematic (not consuming stdout fast enough, throwing weird file descriptor errors, etc), so we wanted to call the executables directly, while retaining a test wrapper option.

[angerman]

@michaelpj, yes that‘s what I initially implemented to allow using cabal test. With component builds we know the text executable and can execute it directly instead of going through cabal and having to deal with the bugs that seem to be stdout/stderr redirection.

It would be great if we could fix this in cabal proper. I did look into this, hoping it could be fixed quickly, but didn’t get anywhere fast.

The approach taken here seems to actually even be superior to running it through cabal, as it removes one layer of indirection.

[rvl]

In Haskell.nix, I think it would be good if the derivation that executes a test suite were separated from the derivation that builds the test suite. (Sometimes we might want to build the tests but run them only nightly, or sometimes we might not want to bother with tests under wine, and instead just execute them on a real windows 10 VM).

And it would also be good to have a way of generically overriding all component derivations. For example, if hostPlatform = windows and componentType = test then override the checkPhase so that tests are run under wine.

[angerman]

@rvl right that splitting would be a great addition. But seems orthogonal to this implementation.