Build time over travis time limit again

[Andrey Mokhov]

Hi Joachim,

> Does Hadrian speed up a build from scratch?

Hadrian can build GHC on Windows (AppVeyor) and Linux (Travis) CI instances in about 40 mins using the 'quickest' build flavour (no optimisation/docs). 

https://ci.appveyor.com/project/snowleopard/hadrian
https://travis-ci.org/snowleopard/hadrian

On Travis OSX we recently started to time out (jobs are terminated at 48 mins), even though I'm using another trick to save build time on OSX: building with the --integer-simple flag, which skips building the GMP library.

Cheers,
Andrey