mxcl/homebrew — pull request #14455 by 2bits (2012-08-25 23:10:16+00:00)
Title: ghc: 7.4.2 build from source, internal cabal-install

Following the discussion in #13519, ghc gets a major overhaul:

* Add a subformula that installs the ghc binary like before
* Add a subformula to build cabal-install with that ghc
* Use both to build ghc from source
* Add code to `rm ~/.ghc ~/.cabal`
* Add code to cabal install happy and alex.
* Force ENV['LD'] = 'ld' to stop an assertion linking with llvm.
* Plant trees.

Fixes #13519