Sorry, I should've specified! This is Swift 5.10. Trying to build Swift 6 failed for me for a host of other reasons, but I was hoping to make both available. I can give Swift 6 another shot (though I was under the impression that Swift 6 doesn't support bootstrapping without having an existing Swift compiler).
If you're aware of the patches and would be able to link them, I can try to backport to 5.10 too!