Separate module to add fields to Bakery settings form

bakery_override.info

name = Bakery Override
description = Appends User Fields to the Bakery setting form
core = 7.x
dependencies[] = bakery

bakery_override.module

<?php
/**
 * Implements hook_form_FORM_ID_alter()
 *
 * Add user fields to Bakery settings form
 */
function bakery_override_form_bakery_settings_alter(&$form, &$form_state, $form_id) {
  $options = array();
  $result = field_info_instances('user');
  foreach ($result['user'] as $field => $data) {
    $options[$field] = check_plain($data['label']);
  }
  $form['bakery_supported_fields']['#options'] = array_merge($form['bakery_supported_fields']['#options'], $options);
}