"I saw the Messenger of Allah in his (constructed) toilet, facing towards the Qiblah." (Da'if) (One of the narrators) 'Eisa said: "I told that to Sha'bi, and he said: 'Ibn 'Umar spoke the truth. As for the words of Abu Hurairah, he said: "In the desert do not face the Qiblah nor turn one's back towards it." As for the words of Ibn 'Umar, he said: "In the (constructed) toilet there is no Qiblah so turn in whatever direction you want."

Another chain with similar wording.
Sunan Ibn Majah Book 1, Hadith 57
← Previous Hadith "People say: 'When you sit to relieve yourself, do not face the Qiblah.' But one day I climbed up onto the roof of our house, and I saw the Messenger of Allah sitting on two bricks (to relieve himself), facing the direction of Baitul-Maqdis (Jerusalem)." This is a Hadith narrated by Yazid bin Harun.

Sunan Ibn Majah Book 1, Hadith 56 Next Hadith → "Mention was made in the presence of the Messenger of Allah of some people who did not like to face towards the Qiblah with their private parts. He said: 'I think that they do that. Turn my seat (in the toilet) to face the Qiblah.'" (Da'if)

Another chain with similar wording.

Sunan Ibn Majah Book 1, Hadith 58