anchor.diff:      buildInputs =
         [ zlib readline openssl libxml2 ]
         ++ lib.optionals icuEnabled [ icu ]
  +      ++ lib.optionals lz4Enabled [ lz4 ]
         ++ lib.optionals enableSystemd [ systemd ]
         ++ lib.optionals gssSupport [ libkrb5 ]
         ++ lib.optionals (!stdenv.isDarwin) [ libossp_uuid ];
  
positive.code:   generic =
        # dependencies
        { stdenv, lib, fetchurl, makeWrapper
        , glibc, zlib, readline, openssl, icu, systemd, libossp_uuid
        , pkg-config, libxml2, tzdata
  
        # This is important to obtain a version of `libpq` that does not depend on systemd.
  
negative.code:   let
      atLeast = lib.versionAtLeast version;
      icuEnabled = atLeast "10";
      lz4Enabled = atLeast "14";
  
    in stdenv.mkDerivation rec {
      pname = "postgresql";
  