You don't want the same company that makes the iPhone to make your enterprise servers. Regardless, it seems I'm stuck with using a small OS X 10.3.9 cluster. We can't upgrade easily (I won't get in to the reasons, though some of them are partly Apple's fault of course), but suffice to say that despite having such a nice machine, we are stuck in the 32 bit land of the not so ancient OS X 10.3 and can't even get things like Java JDK 1.5 or 1.6 (an added incentive to upgrade to OS X 10.4 from Apple...).
At any rate, if you also have these problems (unlikely, but I know some of you are out there), here are the options I used to build GMP 4.2.1 with GCC 4.2.0 (prerelease):
CFLAGS and CXXFLAGS: -O3 -m32 -mcpu=7450 -mpowerpc -maltivec
make distclean && ./configure --enable-cxx ABI=32 && make && make check