Laravel order by has relation

There is a Post model, which has relations PostTags. Relations can be empty. During the search, I need to get posts, which have certain tags(from search) first, and then all other. To retrieve the only posts, which have certain tags, I can use whereHas:

$posts->whereHas(
  'tags', function(Builder $builder) use ($tags) {
     $builder->whereIn('tag_id', $tags);
})

But I need to add the others to the end. Any suggestions on how to do it? Or maybe there is a way to unite whereHas and orderBy?

via Chebli Mohamed