GCC 4.6: Don't bail out when `gnused' isn't provided.

svn path=/nixpkgs/trunk/; revision=33896

pkgs/development/compilers/gcc/4.6/default.nix

@@ -28,7 +28,7 @@
 , gnat ? null
 , libpthread ? null, libpthreadCross ? null  # required for GNU/Hurd
 , stripped ? true
-, gnused
+, gnused ? null
 }:
 
 assert langJava     -> zip != null && unzip != null
@@ -40,6 +40,9 @@ assert langVhdl     -> gnat != null;
 # LTO needs libelf and zlib.
 assert libelf != null -> zlib != null;
 
+# Make sure we get GNU sed.
+assert stdenv.isDarwin -> gnused != null;
+
 with stdenv.lib;
 with builtins;