Add gltk

Rsconscript

@@ -8,6 +8,7 @@ env "app" do |env|
     "libs/bindbc-common/source",
     "libs/bindbc-sdl/source",
     "libs/glad",
+    "libs/gltk",
   ]
   sources = dirs.reduce([]) do |result, dir|
     result + glob("#{dir}/**/*.{d,c}")