message: Add at_init emscripten_environ_constructor
diff: @@ -140,6 +140,10 @@ pub fn run_emscripten_instance(
  let data_ptr = &mut data as *mut _ as *mut c_void;
  instance.context_mut().data = data_ptr;
  + if let Ok(_func) = instance.dyn_func("___emscripten_environ_constructor") {
  + instance.call("___emscripten_environ_constructor", &[])?;
  + }
  +
  let main_func = instance.dyn_func("_main")?;
  let num_params = main_func.signature().params().len();
  let _result = match num_params {
  