I tried building it on OS X recently, and it almost worked, except that libffi a small module to help calling C code from interpreted languages isn't being supported that much right now and hasn't been ported to intel OS X yet.
So the logical solution would be to try and figure out what that bit of assembly code was doing and port it.
But that's no fun.
So instead I had the odd idea of replacing gnucash's current the scheme interpreter guile, with mono (An open source .NET environment). This would cut the dependency on the old libffi (by replacing it with a new large complicated but hopefully more maintained dependency) and more importantly for me, make it easier to muck around with my finances by writing python code instead of scheme code.
Of course building mono on OS X hasn't been trivial, and I haven't even gotten gtk-sharp to work yet.