Enqueue script inside IE conditional comments

Change

<!--[if (gte IE 6)&(lte IE 8)]>
  <?php
    function blarg(){
      wp_enqueue_script('selectivizr', get_template_directory_uri() . 'assets/js/vendor/selectivizr.js');
    }
    add_action('wp_enqueue_scripts', 'blarg', 101);
  ?>
  <![endif]-->

to

<!--[if (gte IE 6)&(lte IE 8)]>

<script src="<?php echo get_template_directory_uri(); ?>/assets/js/vendor/selectivizr.js" type="text/javascript"></script>

<![endif]-->

wp_enqueue_script() should only be used in a functions.php file.