Use a function that returns an array of arrays that the options
field expects.
Something like this (untested code):
array(
'name' => 'Test Select',
'desc' => 'field description (optional)',
'id' => $prefix . 'test_select',
'type' => 'select',
'options' => get_myposttype_options('myposttype'),
),
function get_myposttype_options($argument) {
$get_post_args = array(
'post_type' => $argument,
);
$options = array();
foreach ( get_posts( $get_post_args ) as $post ) {
$title = get_the_title( $post->ID );
$options[] = array(
'name' => $title,
'value' => $title,
);
}
return $options;
}