Prevent building llvm@8: with an incompatilble gcc (#11220)
Prevent building llvm@8: with an incompatilble gcc (#11220)


LLNL/spack,iulian787/spack,LLNL/spack,iulian787/spack,iulian787/spack,iulian787/spack,LLNL/spack,LLNL/spack,LLNL/spack,iulian787/spack