Allow overriding config file options with MANGOHUD_CONFIG if using legacy layout

src/overlay_params.cpp

@@ -667,9 +667,13 @@ parse_overlay_config(struct overlay_params *params,
 
    }
 
+   // TODO decide what to do for legacy_layout=0
    // second pass, override config file settings with MANGOHUD_CONFIG
-   // if (env && read_cfg)
-   //    parse_overlay_env(params, env);
+   if (params->enabled[OVERLAY_PARAM_ENABLED_legacy_layout] && env && read_cfg) {
+      // If passing legacy_layout=0 to MANGOHUD_CONFIG anyway then clear first pass' results
+      HUDElements.ordered_functions.clear();
+      parse_overlay_env(params, env);
+   }
 
    if (is_blacklisted())
       return;