If you put -stdlib=libc++ in CXXFLAGS, graphite2 1.2.0 fails to build with:
/usr/bin/../lib/c++/v1/utility:255:15: error: no viable overloaded '='
first = __p.first;
as reported to the MacPorts project here:
This is not a problem on shipping versions of OS X because they use libstdc++ as the standard library.