CircleCI can't build on OS X
As mentioned in [https://github.com/ghc/ghc/pull/83] CircleCI seems to have trouble with OS X builds. They invariably end in one of a few ways,
- it hangs
- it is "cancelled" with CircleCI issuing the vague warning that there was "an issue while running this container"
Fuuzetsu has raised the issue with CircleCI support.