Add an actual clippy error on all platforms

src/error_handling.rs

@@ -21,6 +21,7 @@ fn show_error(explanation: &str) -> ! {
 }
 
 pub fn show_nvim_error(msg: &str) {
+    let msg = msg;
     send_ui(ParallelCommand::ShowError {
         lines: msg.split('\n').map(|s| s.to_string()).collect_vec(),
     });