Add support for macOS Big Sur (#17236)
Add support for macOS Big Sur (#17236)

* Add support for macOS Big Sur

* Big Sur is actually macOS 11.0
LLNL/spack,LLNL/spack,iulian787/spack,LLNL/spack,iulian787/spack,LLNL/spack,iulian787/spack,LLNL/spack,iulian787/spack,iulian787/spack