anchor.diff:      # Programs exit with code 1 when testing help, so grep for a string
       set +o pipefail
       qjs     --help 2>&1 | grep "QuickJS version"
  -    qjsbn   --help 2>&1 | grep "QuickJS version"
       qjscalc --help 2>&1 | grep "QuickJS version"
       set -o pipefail
   
  
positive.code: 
  stdenv.mkDerivation rec {
    pname = "quickjs";
    version = "2019-12-21";
  
    src = fetchurl {
      url = "https://bellard.org/${pname}/${pname}-${version}.tar.xz";
      sha256 = "13hlx6qwrrxmlvvqcr3irxba6zmf05cf54l32vj50wc66s1qd41p";
    };
  
    makeFlags = [ "prefix=${placeholder "out"}" ];
  
negative.code:     echo "console.log('Output from compiled program');" > "$temp"
      set -o verbose
      out=$(mktemp) && qjsc         "$temp" -o "$out" && "$out" | grep -q "Output from compiled program"
      out=$(mktemp) && qjsc   -flto "$temp" -o "$out" && "$out" | grep -q "Output from compiled program"
    '';
  
    meta = with lib; {
  