Cmake will just disable documentation of it doesn't find doxygen. And if doxygen doesn't find LaTeX, it should just skip the formulas.
Anyway, use cmake with the -DENABLE_DOXYGEN=OFF flag.
More importantly, don't build GNU Radio on the pi itself. The raspberry pi is an embedded device, not a compilation platform, to be honest. RAM will quickly become a bottleneck, and together with the limited storage bandwidth that means that even if successful, the build will take days.
Instead, spend that time on fixing whatever is wrong with the packet. I do happen to know the maintainer of the Debian gnuradio packages, and he's a really nice guy. If you can write a good bug report, I'm sure he, or the GNU Radio mailing list, will figure something out.