What is the ruling in the Hanafi school regarding facing or turning one's back to the Qiblah while inside a closed restroom building?

It is completely permissible because there are walls separating the person from the Ka'bah.
It is Makruh Tahrimi (prohibitively disliked), just like in an open desert.
It is highly recommended.
It is only disliked for women, not for men.