VTK package: don't require "+llvm" for mesa dependency (#9256)
VTK package: don't require "+llvm" for mesa dependency (#9256)


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