On my dual G5, I can build GNU make 3.80 from source in 4s. Which means I can build it from source every time I run it and still be pretty competitive with Ant's performance.
Of course, it sucks that I have to build from source to get a version of GNU make released in 2002, but I filed a bug report with Apple for that earlier this year.
Also built from source so far: GNU grep 2.5.1 (which thanks to the current state of GNU grep, I had to get from Debian!), Jikes 1.22, and Subversion. Coming soon: Exuberant ctags.
Turns out there's no readlink(1) on a fresh Mac OS install, either. I don't know what to do about that. Most of my Java programs use that to cope with users running them via symbolic links.