Disable assert_unsafe_precondition to measure compile-time cost

Author: saethlin

library/core/src/ub_checks.rs

@@ -69,9 +69,11 @@ macro_rules! assert_unsafe_precondition {
                 }
             }
 
+            if cfg!(debug_assertions) {
             if ::core::ub_checks::$kind() {
                 precondition_check($($arg,)*);
             }
+            }
         }
     };
 }