Add TODO(#4)

nobuild.h

@@ -221,7 +221,7 @@ void mkdirs_impl(int ignore, ...)
 #define MKDIRS(...) mkdirs_impl(69, __VA_ARGS__, NULL)
 
 // TODO(#3): there is no way to remove a folder
-// TODO: there is no way to remove a file
+// TODO(#4): there is no way to remove a file
 
 const char *concat_impl(int ignore, ...)
 {