Antifragility for most real world software means that the quality has to improve over time even though requirements are changing. Unless the software is adapting itself to new requirements (as well as maintaining itself), that means that the net outcome of development and maintenance efforts has to be an improvement in quality. While the design of the software can be a major factor here (making antifragility easier to achieve or harder), it still depends on the system outside of the software that is developing and maintaining it.
> I don't know if that's a hard problem, but that's a meta-programming problem.
I'd suggest its a problem equivalent to solving strong AI.
> Not something you can do easily if you don't use lisp.
Lisps aren't the only class of languages that support easy metaprogramming, and language support for easy metaprogramming doesn't do much to get you closer to the goal here, anyway.
Software itself might be able to, though I suspect that's a hard problem, in the technical sense. Software considered in conjunction with the social system surrounding it which provides maintenance, etc., certainly can be, but that's a social problem rather than a technical one (and, really, the solutions to it are pretty much the same as making the social system better even if the processes it was managing are not automated.)