r9968/sofa : cmake: fixed build with gcc<4.6 when gcc4.6 is present on the system
r9968/sofa : cmake: fixed build with gcc<4.6 when gcc4.6 is present on the system


Former-commit-id: 8c7ebf1b7386f2546cb3a8aa2f1f3b8946af9e16
FabienPean/sofa,FabienPean/sofa,FabienPean/sofa,FabienPean/sofa,Anatoscope/sofa,hdeling/sofa,Anatoscope/sofa,Anatoscope/sofa,FabienPean/sofa,FabienPean/sofa,hdeling/sofa,Anatoscope/sofa,Anatoscope/sofa,hdeling/sofa,hdeling/sofa,FabienPean/sofa,hdeling/sofa,hdeling/sofa,Anatoscope/sofa,FabienPean/sofa,hdeling/sofa,hdeling/sofa,FabienPean/sofa,Anatoscope/sofa,hdeling/sofa,hdeling/sofa,FabienPean/sofa,Anatoscope/sofa,Anatoscope/sofa