So, first the build steps:
tar xvf gdb-7.6.1.tar.bz
rm -rf intl texinfo/ sim
../gdb-7.6.1/configure --target mips-TiVo-linux --prefix ~/tivo/tools/mips-tivo --with-lib-iconv-prefix=/usr/local --without-expat
It took a little bit of dorking around to find all the details, but the FreeBSD gdb port gave some good hints.
But this versions must be too new :(. All the core files I was able to generate failed to get a good traceback.
So, I'll give it another shot with an older gdb.