The system Rust uses is closer to imake than autoconf: the compiler knows what system its building for and sets attributes to let the code know what it should use. (The imake style is a little less flexible than autoconf, but no less insane. Six of one, half a dozen of the other.)

For example:

    cfg_if! {
      if #[cfg(windows)] {
        mod windows;
        pub use windows::*;
      } else {
        mod unix;
        pub use unix::*;
      }
    }

The 13 struct stat's in libc: https://github.com/rust-lang-nursery/libc/search?utf8=%E2%9C...

Cargo supports versioning libraries (and seemingly does so sanely!). Obscure platform support is obscure.