spidermonkey_{31,38}: fix sed problem with build

pkgs/development/interpreters/spidermonkey/31.nix

···
-{ stdenv, fetchurl, pkgconfig, perl, python2, zip, libffi, nspr, icu, readline }:
+{ stdenv, fetchurl, pkgconfig, gnused_422, perl, python2, zip, libffi, nspr, icu, readline }:
 
 stdenv.mkDerivation rec {
   version = "31.5.0";
···
     sha256 = "1q8icql5hh1g3gzg5fp4rl9rfagyhm9gilfn3dgi7qn4i1mrfqsd";
   };
 
-  buildInputs = [ pkgconfig perl python2 zip libffi readline nspr icu ];
+  buildInputs = [ libffi readline nspr icu ];
+  nativeBuildInputs = [ pkgconfig perl python2 zip gnused_422 ];
 
   postUnpack = "sourceRoot=\${sourceRoot}/js/src";
 

pkgs/development/interpreters/spidermonkey/38.nix

···
-{ stdenv, fetchurl, pkgconfig, perl, python2, zip, libffi, readline, icu, zlib, nspr }:
+{ stdenv, fetchurl, pkgconfig, gnused_422, perl, python2, zip, libffi, readline, icu, zlib, nspr }:
 
 stdenv.mkDerivation rec {
   version = "38.2.1.rc0";
···
     sha256 = "0p4bmbpgkfsj54xschcny0a118jdrdgg0q29rwxigg3lh5slr681";
   };
 
-  buildInputs = [ pkgconfig perl python2 zip libffi readline icu zlib nspr ];
+  buildInputs = [ libffi readline icu zlib nspr ];
+  nativeBuildInputs = [ pkgconfig perl python2 zip gnused_422 ];
 
   postUnpack = "sourceRoot=\${sourceRoot}/js/src";