Question, is there any reason why you can't use /usr/bin/gcc instead? It's gcc 4.2.

I switched to xcode 4 so I'll explain it with version 4. You can always upgrade. The process might be a little different in 3.2, not sure.

You can switch the compiler in xcode 4 by going to the Build setting for your target. One of the options is Compiler Version and you can switch it from LLVM compiler 2.0, the default in xcode 4, to gcc 4.2 which will target /usr/bin/gcc.

You can also create a project with an External Build System and use make. That will give you full control of the build and you can use whatever you want for compiler but that's a lot more work.