This is bug 22979 remanifesting. That got a fix, but I'm doing a build of the whole of Xorg using jhbuild and it just tried to build it ...
Kernel: Linux lt9400 2.6.31-17-generic #54-Ubuntu SMP Thu Dec 10 17:01:44 UTC 2009 x86_64 GNU/Linux
OS: Ubuntu 9.10 x86-64
Expected: should see it's doing a 64-bit build and not even attempt it.