display dynamic WP Site logo on wp-admin using CSS

I'm looking for a way to always display the current site logo (as set in customiser) on the wp-admin page in place of the WP logo via CSS. I know how to manually add a custom image (code below is part of the function I use):

    #login h1 a, .login h1 a {
          background-image: url(?php echo get_stylesheet_directory_uri(); ?/images/logo.png); background-size: contain;

But I would like to make the entire URL dynamic, so the site logo can be changed in the customiser and automatically update the login page, too.

Any ideas/solutions?