Incompatible with Linux

[amuniz]

A few workarounds were needed to make the installation proceed in Linux:

1. hermit init fails with text file busy: I ran hermit init myself from the upper directory, then moved the generated files into .hermit-working/bin
2. sw_vers is MacOS specific: I created my own sw_vers for Ubuntu which produces a compatible output

But then:

Resolved 161 packages in 647ms
  × Failed to build `pyobjc-framework-coreml==11.1`
  ├─▶ The build backend returned an error
  ╰─▶ Call to `setuptools.build_meta.build_wheel` failed (exit status: 1)

      [stdout]
      running bdist_wheel
      running build

      [stderr]
      error: This distribution is only supported on macOS >= 10.13

      hint: This usually indicates a problem with the package or the build environment.
  help: `pyobjc-framework-coreml` (v11.1) was included because `ocrmac` (v1.0.0) depends on `pyobjc-framework-vision` (v11.1) which depends on `pyobjc-framework-coreml`

The project depends on libraries that seem to be supported for MacOS only.