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: , zlib
  
  , channel
  }:
  
  # >=45.0.0 should use the releases in the murcurial repo at:
  
negative.code: let
    inherit (lib)
      optionals
      optionalString
      replaceStrings
      versionAtLeast;
  
  