Copy executables by default on windows.

[AndreasPK]

---

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• [ x] Patches conform to the coding conventions.
• [ x] Any changes that could be relevant to users have been recorded in the changelog.
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Running cabal install on windows.

[AndreasPK]

CI error seems unrelated to the patch as far as I can tell.

[phadej]

I'll take over this. I'd add a auto mode, which would behave as copy on windows and symlinks everywhere else, that's so you could configure explicitly the default behavior.

Later that can be extended so windows mode could symlink if that's possible (pending @Mistuke's advice on how to recognize that).

I'll also fix the changelog, but first have to try to fix that failing test, as it fails way too often.

[phadej]

Merged as part of #6519