zimreader: Broken on i686

(Well, actually tntnet, but that derivation is defined in the same file).
http://hydra.nixos.org/build/38238028

pkgs/tools/text/zimreader/default.nix

@@ -39,6 +39,6 @@ in stdenv.mkDerivation rec {
     description = "A tool to serve ZIM files using HTTP";
     homepage = http://git.wikimedia.org/log/openzim;
     maintainers = with stdenv.lib.maintainers; [ robbinch ];
-    platforms = with stdenv.lib.platforms; linux;
+    platforms = [ "x86_64-linux" ];
   };
 }