Windows-4.7.4/mkspecs/features/win32/ltcg.prf

CONFIG(release, debug|release) {
    QMAKE_CFLAGS *= $$QMAKE_CFLAGS_LTCG
    QMAKE_CXXFLAGS *= $$QMAKE_CXXFLAGS_LTCG
    QMAKE_LFLAGS *= $$QMAKE_LFLAGS_LTCG
}