On 14 Jul 2012, David C. Rankin verbalised:
It was either Arch or glibc 2.16 upstream, and it was the missing link in the search locations Nix provided. To solve the issue, I simply created a symlink /lib/cpp->/usr/bin/cpp and tdebase built fine.
<rant> Just for the next two months, I wish upstream would QUIT DORKING WITH THE DAMN PACKAGES!!! </rant>
Actually nothing upstream installs /lib/cpp anymore. It's supposed to be a traditional C preprocessor (non-token-based), unused by GCC for many years since -traditional mode was dropped, but kept on for the sake of other programs that used the C preprocessor to preprocess non-C code. It was believed that its last users were imake and the Xresources parser: it looks like we've found another one, in glibc no less.
I'm fairly sure a patch to glibc changing the path to cpp used by rpcgen would be accepted (even though glibc's rpcgen is semi-deprecated), and shall write one shortly. (But of course this won't show up until glibc 2.17.)