m4: fixed macOS version identification on patch (#13623)
m4: fixed macOS version identification on patch (#13623)

Patch was not being applied in recent versions of macOS. Homebrew is still applying patch to any version after High Sierra.
iulian787/spack,LLNL/spack,LLNL/spack,LLNL/spack,iulian787/spack,LLNL/spack,iulian787/spack,iulian787/spack,LLNL/spack,iulian787/spack