Docker example should work on Darwin

[avdv]

Is your feature request related to a problem? Please describe. The docs mention: https://github.com/tweag/rules_haskell/blob/8a59b40b8208ec9b82b9ded914f8ade9e18946e8/docs/haskell-use-cases.rst?plain=1#L1203-L1206

But the referenced issue is long resolved.

Describe the solution you'd like Check if the example builds on Darwin and update the docs.

Describe alternatives you've considered

Additional context