Move metadata header and version checks together

This will make it easier to report rustc versions for older metadata
formats.

compiler/rustc_driver_impl/src/lib.rs

@@ -676,6 +676,7 @@ fn list_metadata(early_dcx: &EarlyDiagCtxt, sess: &Session, metadata_loader: &dy
                 metadata_loader,
                 &mut v,
                 &sess.opts.unstable_opts.ls,
+                sess.cfg_version,
             )
             .unwrap();
             safe_println!("{}", String::from_utf8(v).unwrap());