Can Qt 5 be built by gcc-4.9 brew on Mac OSX?

[xalloc]

For some reasons, I'm trying to build Qt 5.5 using gcc-4.9 (brew version) on OS X, El Capitan.

First, I overriden /usr/bin/{gcc|g++|cc|c++} to /usr/local/Cellar/gcc49/4.9.3/bin/g++-4.9.

I used -platform macx-g++ when I run ./configure. However, it seems that configure and make keep using /Applications/Xcode.app/Contents/Developer/usr/bin/g++, which binds to clang++.

I enforced QMAKE_CXX variable to point to brew g++. In qtbase/mkspecs/common/g++-base.conf, I'm having the followings:

	QMAKE_COMPILER      = /usr/local/Cellar/gcc49/4.9.3/bin/gcc-4.9

	QMAKE_CC            = /usr/local/Cellar/gcc49/4.9.3/bin/gcc-4.9

	QMAKE_LINK_C        = $$QMAKE_CC
	QMAKE_LINK_C_SHLIB  = $$QMAKE_CC

	QMAKE_CXX           = /usr/local/Cellar/gcc49/4.9.3/bin/g++-4.9

	QMAKE_LINK          = $$QMAKE_CXX
	QMAKE_LINK_SHLIB    = $$QMAKE_CXX

I'm still failing to use brew gcc-4.9 and g++-4.9. What should I do? Is it impossible to use brew's gcc toolchain to build Qt on OS X?