Cabalize the haskell build
Use the cabal artifact in the build

This assumes the user has built the light-haskell artifact already, with
something like:

cabal sandbox init && cabal install --dependencies-only && cabal build

We'll probably want to automate this somehow, or at least warn users
that they need to do this.
Small run script for cabalized build
Replace prebuild binary with bootstrapping shell script
FIX: set cwd correctly for script
Merge pull request #14 from bkirwi/cabal-build

Cabal build