Build the options form.
Overrides ManyToOne::buildOptionsForm
public function buildOptionsForm(&$form, &$form_state) {
parent::buildOptionsForm($form, $form_state);
$form['set_breadcrumb'] = array(
'#type' => 'checkbox',
'#title' => t("Set the breadcrumb for the term parents"),
'#description' => t('If selected, the breadcrumb trail will include all parent terms, each one linking to this view. Note that this only works if just one term was received.'),
'#default_value' => !empty($this->options['set_breadcrumb']),
);
}