No dark magic as far as I recall (except in the actual bundling as a Mac app, unfortunately that required some magic, the GTK libraries don't relocate so easily :-( ). I didn't have any problems building. I compiled it with ghc 7.6.1, with the GTK libraries installed manually (there are some suggestions on how to do that at the very end of my Comprehensive Haskell Sandboxes post,
http://www.edsko.net/2013/02/10/comprehensive-haskell-sandboxes/). It used to be a lot more painful (requiring the latest versions of Haskell libraries, with patches etc.) but these days the situation is a lot better. (That's not so say that problems like the one you reported don't still crop up from time to time, and can cause many a sleepless night..).