[Feature request]: support terminal SIGWINCH on MacOS

[ihexon]

On macOS, the console does not respond to SIGWINCH signals, which leads to a poor terminal experience. It appears that the sigwinch_handler is only registered on Linux 😢

    #[cfg(target_os = "linux")]
    register_sigwinch_handler(console.lock().unwrap().get_sigwinch_fd())
        .map_err(RegisterFsSigwinch)?;

[slp]

Looks like most terminal emulators on macOS do send SIGWINCH and SIGINT just as expected. Sadly, we depend on vmm-sys-util to register signal handlers, and this crate doesn't expose this functionality to macOS.

I've created this PR to tackle this: rust-vmm/vmm-sys-util#263

If/once this gets merged, we'll be able to support SIGWINCH on macOS.