mesa: Restrict llvm to < 11 (#19393)
mesa: Restrict llvm to < 11 (#19393)


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