GNU make built-in rule to Compiling C++ programs with ‘$(CXX) $(CPPFLAGS) $(CXXFLAGS) -c’. To align to it, add empty BUILD_CXXFLAGS in cpp rule. Cc: Giri P Mudusuru <giri.p.mudusuru@intel.com> Cc: Yonghong Zhu <yonghong.zhu@intel.com> Contributed-under: TianoCore Contribution Agreement 1.0 Signed-off-by: Liming Gao <liming.gao@intel.com> Reviewed-by: Giri P Mudusuru <giri.p.mudusuru@intel.com> Reviewed-by: Yonghong Zhu <yonghong.zhu@intel.com>