install.in: cp -p fails when installing on NFS

[jsoo1]

Describe the bug

When using the standard installer at https://nixos.org/nix/install on NFS with a multi-user install, cp -p dies with the following:

error: removing extended attribute 'system.nfs4_dacl' from '...': Invalid argument

The -p argument preserves extended attrs and acls. Some of them might be incompatible between source and target file systems. Generally we should avoid adding -p since we probably should not care about xattrs or acls on installed artifacts, right?

Steps To Reproduce

With an nfs4 filesystem mounted at the destination for the nix store, run https://nixos.org/nix/install.

Expected behavior

The installer should work on NFS.

Metadata

Attempting to install 2.29.0

Checklist

• checked latest Nix manual (source)
• checked open bug issues and pull requests for possible duplicates

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