anchor.diff:  { stdenv, lib, buildPackages
  -, autoreconfHook, texinfo, fetchurl, perl, xz, libiconv, openssl, gmp ? null
  +, autoreconfHook, texinfo, fetchurl, perl, xz, libiconv, gmp ? null
   , hostPlatform, buildPlatform
   , aclSupport ? false, acl ? null
   , attrSupport ? false, attr ? null
  
positive.code:     ];
  
  
    buildInputs = [ gmp openssl ]
      ++ optional aclSupport acl
      ++ optional attrSupport attr
      ++ optionals hostPlatform.isCygwin [ autoreconfHook texinfo ]   # due to patch
  
negative.code:   outputs = [ "out" "info" ];
  
    nativeBuildInputs = [ perl xz.bin ];
    configureFlags =
      optional (singleBinary != false)
        ("--enable-single-binary" + optionalString (isString singleBinary) "=${singleBinary}")
      ++ optional hostPlatform.isSunOS "ac_cv_func_inotify_init=no"
      ++ optional withPrefix "--program-prefix=g"
  