anchor.diff:    outputs = [ "out" "dev" "lib" "man" "doc" ]
       ++ stdenv.lib.optional (pam != null) "pam";
   
  -  nativeBuildInputs = [ perl ];
  +  nativeBuildInputs = [ perl buildPackages.stdenv.cc ];
   
     buildInputs = [ pam ];
   
  
positive.code: { stdenv, fetchurl, attr, perl, pam ? null }:
  assert pam != null -> stdenv.isLinux;
  
  stdenv.mkDerivation rec {
  
negative.code:   makeFlags = [
      "lib=lib"
      (stdenv.lib.optional (pam != null) "PAM_CAP=yes")
      "BUILD_CC=${buildPackages.stdenv.cc.targetPrefix}gcc"
      "CC=${stdenv.cc.targetPrefix}gcc"
    ];
  
    prePatch = ''
  