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).
- The hand written `perlPackages.SearchXapian` bindings have been dropped in favor of the (mostly compatible)
`perlPackages.Xapian`.
- The `nixLog*` family of functions made available through the standard environment have been rewritten to prefix messages with both the debug level and the function name of the caller.
The `nixLog` function, which logs unconditionally, was also re-introduced and modified to prefix messages with the function name of the caller.
For more information, [see this PR](https://github.com/NixOS/nixpkgs/pull/370742).