[PD] compiling (adding objs to) GEM on OS X-- seeking advice

[zack]

I would like to compile some additional GEM objects for OS X.   Has 
anyone out there done this?
  I assume that doing so requires setting up a  compilable version of 
GEM on my Mac OS X machine first.
This is where I could use a hand, knowing where to find gem-lib for OS 
X, and how to go about getting it all to compile.

Any advice, or links would be appreciated.

--Zack Settel