compiler: add default implementation of openmp_flag() and css11_flag()
compiler: add default implementation of openmp_flag() and css11_flag()

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