I really hope that we will get a libc-free Linux target. Mustang/rsix looks like a great step in this direction, similarly to steed (https://github.com/japaric/steed) before it. But I think that ideally it should be done properly in Rust proper, not in outside projects. Here a relevant issue, but there is not much progress on it: https://github.com/rust-lang/rfcs/issues/2610