openspades: fix build

pkgs/games/openspades/default.nix

@@ -1,7 +1,7 @@
 { lib, stdenv, fetchurl, fetchFromGitHub, fetchpatch, cmake, unzip, zip, file
 , curl, glew , libGL, SDL2, SDL2_image, zlib, freetype, imagemagick
 , openal , opusfile, libogg
-, Cocoa
+, Cocoa, libXext
 }:
 
 stdenv.mkDerivation rec {
@@ -19,7 +19,7 @@ stdenv.mkDerivation rec {
   nativeBuildInputs = [ cmake imagemagick unzip zip file ];
 
   buildInputs = [
-    freetype SDL2 SDL2_image libGL zlib curl glew opusfile openal libogg
+    freetype SDL2 SDL2_image libGL zlib curl glew opusfile openal libogg libXext
   ] ++ lib.optionals stdenv.hostPlatform.isDarwin [
     Cocoa
   ];
@@ -63,6 +63,6 @@ stdenv.mkDerivation rec {
     homepage    = "https://github.com/yvt/openspades/";
     license     = licenses.gpl3;
     platforms   = platforms.all;
-    maintainers = with maintainers; [ abbradar ];
+    maintainers = with maintainers; [ abbradar azahi ];
   };
 }