[CMake] Configure Mac OS X for 32-bit

[Tron Thomas]

I am writing a cross platform application using CMake that builds on Mac 
OS X.  I just upgraded to CMake 2.8-1.  When I configure and build my 
project on my Power Mac G5 system running Mac OS X 10.5.8, the project 
builds just fine.

When I try to configure the project on my MacBook Pro running Mac OS X 
10.6.3, I get link errors because the project has been configured to 
build 64-bit applications and some of the needed libraries and 
frameworks the project links with are only 32-bit.

How can I configure my CMake scripts so that the project will build a 
32-bit application on my MacBook Pro?