allow(clippy): single_match for signal handler

Should get more matches in the future.

src/common/os_input_output.rs

@@ -83,6 +83,7 @@ fn handle_command_exit(mut child: Child) {
 
         for signal in signals.pending() {
             // FIXME: We need to handle more signals here!
+            #[allow(clippy::single_match)]
             match signal {
                 signal_hook::SIGINT => {
                     child.kill().unwrap();