anchor.diff:  
   stdenv.mkDerivation rec {
     pname = "quickjs";
  -  version = "2019-12-21";
  +  version = "2020-11-08";
   
     src = fetchurl {
       url = "https://bellard.org/${pname}/${pname}-${version}.tar.xz";
  -    sha256 = "13hlx6qwrrxmlvvqcr3irxba6zmf05cf54l32vj50wc66s1qd41p";
  +    sha256 = "0yqqcjxi3cqagw184mqrxpvqg486x7c233r3cp9mxachngd6779f";
     };
   
     makeFlags = [ "prefix=${placeholder "out"}" ];
  
positive.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) && qjsbnc       "$temp" -o "$out" && "$out" | grep -q "Output from compiled program"
      out=$(mktemp) && qjsc   -flto "$temp" -o "$out" && "$out" | grep -q "Output from compiled program"
      out=$(mktemp) && qjsbnc -flto "$temp" -o "$out" && "$out" | grep -q "Output from compiled program"
    '';
  
    meta = with lib; {
  
negative.code:     # Programs exit with code 1 when testing help, so grep for a string
      set +o pipefail
      qjs     --help 2>&1 | grep "QuickJS version"
      qjscalc --help 2>&1 | grep "QuickJS version"
      set -o pipefail
  
  