gtest: fixed compliation on osx/clang
gtest: fixed compliation on osx/clang

Former-commit-id: 75d902d4331dbd86d1fa349275e5bc9cd13b863f
FabienPean/sofa,Anatoscope/sofa,FabienPean/sofa,FabienPean/sofa,Anatoscope/sofa,FabienPean/sofa,hdeling/sofa,hdeling/sofa,Anatoscope/sofa,Anatoscope/sofa,FabienPean/sofa,FabienPean/sofa,Anatoscope/sofa,hdeling/sofa,Anatoscope/sofa,hdeling/sofa,hdeling/sofa,FabienPean/sofa,Anatoscope/sofa,Anatoscope/sofa,FabienPean/sofa,Anatoscope/sofa,hdeling/sofa,hdeling/sofa,hdeling/sofa,hdeling/sofa,FabienPean/sofa,hdeling/sofa,FabienPean/sofa