use __typeof instead of typeof to compile for Cxx instead of GNUxx

Classes/GlobalStateExplorers/FileBrowser/FLEXFileBrowserController.m

@@ -321,7 +321,7 @@
 #if FLEX_AT_LEAST_IOS13_SDK
 
 - (UIContextMenuConfiguration *)tableView:(UITableView *)tableView contextMenuConfigurationForRowAtIndexPath:(NSIndexPath *)indexPath point:(CGPoint)point __IOS_AVAILABLE(13.0) {
-    __weak typeof(self) weakSelf = self;
+    __weak __typeof__(self) weakSelf = self;
     return [UIContextMenuConfiguration configurationWithIdentifier:nil
                                                    previewProvider:nil
                                                     actionProvider:^UIMenu * _Nullable(NSArray<UIMenuElement *> * _Nonnull suggestedActions) {