Creating new_reference using $(DERIVED_FILE_DIR) not supported

when creating a new reference where the path name is starting with an xcode variable like $(DERIVED_FILE_DIR)/somefile.mm, the path will be treated like a relative path.

Using :absolute to overwrite this behaviour fails with an exception, because the path was not considered absolute.

My current work around is to prefix the path with / when creating the reference and the set the path instance variable of the new ref back to the path without the prefix.