Before building on Mac OS for the first time, you need to install the dependencies:
I followed these steps on 10.6 Snow Leopard and 10.7 Lion. You can probably get it to work (perhaps with slight changes) on 10.5 Leopard. I failed to get jhbuild to work at all on 10.4 Tiger.
I started here:
(Note: I haven’t got PyInstaller working yet on the Mac. 64-bit Mac OS is not supported in PyInstaller 1.5..1, but is supported in the latest git versions. But they have other problems. Still working on it. When it’s done, Mac will be an easy install like Windows.)