Fix overcapturing, unsafe extern blocks, and new unsafe ops

compiler/rustc/src/main.rs

@@ -65,7 +65,7 @@ fn main() {
         // linking, so we need to explicitly depend on the function.
         #[cfg(target_os = "macos")]
         {
-            extern "C" {
+            unsafe extern "C" {
                 fn _rjem_je_zone_register();
             }