Compiling Qt5.3 from source on Mac with g++ 4.9

I’ve got code that relies on features in g++ 4.8 and would like to statically link. So, I need to compile Qt from source with the same compiler I use to compile the rest of my code. Using Homebrew, I installed g++ 4.9 and created a symlink so that g++ maps to g++-4.9 instead of the normal llvmgcc42. However, when I go to configure the Qt build, I’m unsure what -platform argument to use. It appears that the macx specific .conf files are made for llvmgcc42 (see in common/g++-macx.conf there is the line “QMAKE_XCODE_GCC_VERSION = com.apple.compilers.llvmgcc42”). Any recommendations for how can I build from source with g++4.9 on Mac 10.9? Thanks!