The hook can be disabled by providing `dontCheckForBrokenSymlinks = true;` as an argument to `mkDerivation`.
For more information, [check the docs](https://nixos.org/manual/nixpkgs/unstable/#no-broken-symlinks.sh) or [see this PR](https://github.com/NixOS/nixpkgs/pull/370750).
-`opensmtpd-extras` has been deprecated by upstream and is not compatible with
OpenSMTPD 7.6.0 or later. The package has been removed in favor of a set of new
`opensmtpd-table-*` packages.
- The hand written `perlPackages.SearchXapian` bindings have been dropped in favor of the (mostly compatible)