small fixes relating to alex, happy, and hlint build steps

fix cabal and happy build step error reporting

one small caveat is that if cabal is configured to generate alex and happy parsers, then the errors could be reported twice.


run hlint with working dir set to project root

this lets HLint.hs file for configuring hlint live in the project dir, which I feel is more natural than peppering them in every subdirectory.