there is a discussion on the RHBZ, about -Werror option.
The conclusion, from my POV as a maintainer is, that -Werror flag is should be removed from stable released tarballs. It breaks things, when teh environments is changing, which is quite often in Fedora.
One way or another, I'd be gratefull for a fast decission (if I can wait for next version, or If I should fix it through SPEC file downstream way)
In comment 14 the observation is pointed out, that -Werror is maybe currently used only for PerconaFT sub-directory.