Fix issue with gcc 5.x not building on RHEL6
Fix issue with gcc 5.x not building on RHEL6

EmreAtes/spack,iulian787/spack,lgarren/spack,skosukhin/spack,matthiasdiener/spack,mfherbst/spack,TheTimmy/spack,LLNL/spack,LLNL/spack,skosukhin/spack,tmerrick1/spack,EmreAtes/spack,mfherbst/spack,krafczyk/spack,tmerrick1/spack,LLNL/spack,matthiasdiener/spack,mfherbst/spack,skosukhin/spack,EmreAtes/spack,skosukhin/spack,mfherbst/spack,lgarren/spack,krafczyk/spack,TheTimmy/spack,tmerrick1/spack,EmreAtes/spack,LLNL/spack,EmreAtes/spack,lgarren/spack,TheTimmy/spack,iulian787/spack,tmerrick1/spack,skosukhin/spack,krafczyk/spack,iulian787/spack,lgarren/spack,krafczyk/spack,krafczyk/spack,TheTimmy/spack,matthiasdiener/spack,matthiasdiener/spack,TheTimmy/spack,mfherbst/spack,matthiasdiener/spack,iulian787/spack,LLNL/spack,iulian787/spack,lgarren/spack,tmerrick1/spack