Fix 'make clean'

APP_NODE_MODULE_DIRS contains two paths. Quoting that var breaks
the command and the node_module folders were not deleted.

Makefile

@@ -33,7 +33,7 @@ $(LOCAL_DIR)/%/:
 .PHONY: clean
 clean:
 	rm -rf \
-		"$(APP_NODE_MODULE_DIRS)" \
+		$(APP_NODE_MODULE_DIRS) \
 		"$(TEMP_DIR)" \
 		"$(LOCAL_DIR)/dist"