Build breakage with spack on OSX

[balay]

/Users/balay/spack/lib/spack/env/clang/clang++    --std=c++11 -O2 -g -fno-omit-frame-pointer -ferror-limit=1 -Werror -Weverything -Wno-c++98-compat -Wno-c++98-compat-pedantic -Wno-padded -Wno-float-equal -Wno-weak-template-vtables -O2 -g -DNDEBUG   -o CMakeFiles/gmodel.dir/gmodel.cpp.o -c /Users/balay/spack/var/spack/stage/gmodel-2.1.0-vybj2tmqaue4qh6wa6ige3ndsw5pb7pd/gmodel-2.1.0/gmodel.cpp
/Users/balay/spack/var/spack/stage/gmodel-2.1.0-vybj2tmqaue4qh6wa6ige3ndsw5pb7pd/gmodel-2.1.0/gmodel.cpp:33:21: error: zero as null pointer constant [-Werror,-Wzero-as-null-pointer-constant]
    /* LOOP    = */ 0,
                    ^
                    nullptr
fatal error: too many errors emitted, stopping now [-ferror-limit=]

I think -Werror is useful for deveopers - but should not be required for users.

Does CMAKE take an option to override this?
gmodel-2.1.0-spack-build.out.txt