Add ignore-pass directive to overflowing-ops tests

Author: gurry

tests/ui/lint/lint-overflowing-ops-consts.noopt.stderr

@@ -5,6 +5,7 @@
 //[noopt]compile-flags: -C opt-level=0
 //[opt]compile-flags: -O
 //[opt_with_overflow_checks]compile-flags: -C overflow-checks=on -O
+// ignore-pass (test tests codegen-time behaviour)
 
 
 #[cfg(target_pointer_width = "32")]