Fixed cxx standard for gcc49 + g4r10

Geant4/G4config/CMakeLists.txt

@@ -38,6 +38,13 @@ endif()
 
 set(GEANT4_TAG ${GEANT4_TAG} CACHE STRING "Tag of Geant4 to get from the Geant4-srcs repository")
 
+# Fix the C++ standard for GCC 4.9
+if(${GAUDI_CXX_STANDARD} STREQUAL "c++1y" AND $ENV{CMTOPT} MATCHES "gcc49")
+  set(CXX_STANDARD "c++14")
+else()
+  set(CXX_STANDARD ${GAUDI_CXX_STANDARD})
+endif()
+
 include(ExternalProject)
 
 ExternalProject_Add(Geant4