use of fdupes in build process

I noticed in 1 rpm, there was a comment next to an %fdupes line -- which I guess is a macro(?) saying: # Hardlink duplicate files %fdupes ${RPM_BUILD_ROOT} Is it still used for purposes of hardlinking dupes? If so, how does that work? when I looked at fdupes, I didn't see an option to hardlink dups, only options to delete dups. Anyway, would it be useful if that was about 40% faster?