anchor.diff:      autoconf_21x
       perl
       python2
  -    which
     ];
   
     buildInputs = [
  +    icu
  +    readline
  +    zlib
  +  ] ++ optionals (ctypes) [
       libffi
       nspr
  -    zlib
  -    readline
  -    icu
     ];
  -
  -  postUnpack = ''
  -    srcRoot="$srcRoot/js/src/"
  -  '';
   
     # They assume the autoconf binary is named `autoconf-2.13` so detection fails.
     AUTOCONF = "${autoconf_21x}/bin/autoconf";
  
positive.code: { stdenv
  , autoconf_21x
  , fetchurl
  , fetchzip
  , lib
  , perl
  , python2
  , which
  
  , icu
  , libffi
  
negative.code:     done
    '';
  
    installParallel = false;
  
    passthru = {
  