Make GDNative DLLs work on UWP

modules/gdnative/gdnative.cpp

@@ -130,6 +130,9 @@ bool GDNative::initialize() {
 	// we should pass library name to dlopen(). The library name is flattened
 	// during export.
 	String path = lib_path.get_file();
+#elif defined(UWP_ENABLED)
+	// On UWP we use a relative path from the app
+	String path = lib_path.replace("res://", "");
 #else
 	String path = ProjectSettings::get_singleton()->globalize_path(lib_path);
 #endif