Wait, forgive me if I'm wrong (0 Ruby knowledge!) but isn't this branch the wrong way round? As in, we want to disable SSSE3 on a few 2013 models because there is currently a bug, so we want something like:
    
    args << '-no-ssse3' if MacOS.version <= :snow_leopard  || (is_problematic_2013_model && macOS.version >= :Mavericks)

Won't practically every machine building this [have SSSE3 support](http://en.wikipedia.org/wiki/SSSE3) making the other conditional a mute point?