With sufficient (usually stolen) training data they could probably do it to a state where it's kinda usable in an assistive manner.

Though since these LLMs often struggle with anything that doesn't exist in truly abhorrent abundance in its training data as well as the actual engineering part (i.e. structuring the code sensibly and consistently, which I'd wager is crutially important with Assembly to not end up with spaghetti) trying to have it generate something from scratch would probably end up in a huge mess.