fn get_sigchld_flag() -> Arc<AtomicBool> {
    let flag = Arc::new(AtomicBool::new(false));
    child_process::register_child_hook(flag.clone());

    flag
}
The SIGCHLD can be set by the children of leftwm if their window need a refresh for example.
So we're returning the flag to check when leftwm can be suspended and when not.
Click [here](https://frameboxxindore.com/linux/what-is-sigchld-in-linux.html) for an
example-description.
leftwm/src/bin/leftwm.rs