anchor.diff:  
     buildInputs =
       [ openssl db gettext kerberos ]
  +    ++ lib.optional enableLdap openldap
       ++ lib.optional stdenv.isFreeBSD autoreconfHook
       ++ lib.optional stdenv.isLinux pam
       ++ lib.optional stdenv.isDarwin fixDarwinDylibNames;
  
positive.code: { lib, stdenv, fetchurl, openssl, kerberos, db, gettext, pam, fixDarwinDylibNames, autoreconfHook }:
  
  with stdenv.lib;
  stdenv.mkDerivation rec {
  
negative.code: 
    configureFlags = [
      "--with-openssl=${openssl.dev}"
    ] ++ lib.optional enableLdap "--with-ldap=${openldap.dev}";
  
    # Set this variable at build-time to make sure $out can be evaluated.
    preConfigure = ''
  