Run shortcode in custom script in wp_head if post type is CPT ‘Jobs’

You shouldn’t do it in a shortcode, you should enqueue this particular JavaScript file only for the page you want. Place something like this in your functions.php:

function my_custom_scripts() {
    if( is_singular('job') ){
      wp_enqueue_script('jobpostingschema', get_stylesheet_directory_uri() . '/js/jobpostingschema.js', array(), '', false);
    }
}
add_action('wp_enqueue_scripts', 'my_custom_scripts');