Allow unused_variables lint to placate test failure exposed by macos builders.

Author: pnkfelix

src/test/run-pass/issues/issue-45731.rs

@@ -9,6 +9,7 @@
 // except according to those terms.
 
 // run-pass
+#![allow(unused_variables)]
 // compile-flags:--test -g
 
 #[cfg(target_os = "macos")]