nsnake-2.0.0-1.fc21 is not built with $RPM_OPT_FLAGS. One slightly ugly way to fix it:

    -make CFLAGS="%{optflags}" %{?_smp_mflags}
    +make PLATFORM="%{optflags}" V=1 %{?_smp_mflags}

The V=1 is important there to see from the logs what's going on.
Also from the logs, there's a lot of these:

    sh: dot: command not found

BuildRequires: %{_bindir}/dot would be one way to fix this. On the other hand because the generated documentation is not installed, I think it doesn't need to be generated either and "make doc" along with its dependencies could be dropped.