I managed to forward pages with gclid parameter to a page ending with just “?” by adding this code to wp-cache-phase1.php:
$wp_cache_request_uri = $_SERVER[ 'REQUEST_URI' ]; // Cache this in case any plugin modifies it.
// CHANGE HERE
$wp_cache_request_uri = preg_replace('/gclid=[\w]+&?/i', '', $wp_cache_request_uri);