switch-to-configuration-ng: ensure die() always exits with non-zero code

// Allow for this switch-to-configuration to remain consistent with the perl implementation.

// Perl's "die" uses errno to set the exit code: https://perldoc.perl.org/perlvar#%24%21

fn die() -> ! {

    std::process::exit(std::io::Error::last_os_error().raw_os_error().unwrap_or(1));

    let code = match std::io::Error::last_os_error().raw_os_error().unwrap_or(1) {

        // Ensure that even if errno did not point to a helpful error code, we still have a

        // non-zero exit code

        0 => 1,

        other => other,

    };

    std::process::exit(code);

}

fn parse_os_release() -> Result<HashMap<String, String>> {