core/pkgs/by-name/li/libjpeg-turbo/packages.nix

{ ... }:
res: pkgs: super:

with pkgs; {
  # also known as libturbojpeg
  libjpeg_turbo = callPackage ./. { };
  libjpeg = libjpeg_turbo;
  libjpeg8 = libjpeg_turbo.override { enableJpeg8 = true; };
}