nixpkgs renamed pkgconfig to pkg-config

[rizo]

See https://github.com/NixOS/nixpkgs/pull/109595

error: 'pkgconfig' has been renamed to/replaced by 'pkg-config'

As a workaround, the following override fixes the issue:

  # nix 23.11 renamed `pkgconfig` to `pkg-config`
  conf-pkg-config = super.conf-pkg-config.overrideAttrs (oldAttrs: {
    propagatedBuildInputs = [ pkgs.pkg-config ];
    propagatedNativeBuildInputs = [ pkgs.pkg-config ];
  });

We should add a default overlay for this in onix or submit a fix upstream to opam.

[rizo]

https://github.com/ocaml/opam-repository/blob/d87a1eb8c3d0e6228e3f957b25aa87f49e397d03/packages/conf-pkg-config/conf-pkg-config.3/opam#L19