<no location info>:
Warning: Couldn't figure out LLVM version!
Make sure you have installed LLVM
ghc: could not execute: opt
The ghc documentation
(http://www.haskell.org/ghc/docs/7.6.1/html/users_guide/code-generators.html)
says that llvm and clang are installed by default for 10.6 and
later. I am on 10.8.3.