Added workaround for JSRoutingBundle mkdir issue

[mnocon]

Example failure:

request.CRITICAL: Uncaught PHP Exception ErrorException: 
"Warning: mkdir(): File exists" at /var/www/vendor/friendsofsymfony/jsrouting-bundle/Extractor/ExposedRoutesExtractor.php line 179 
{"exception":"[object] (ErrorException(code: 0): 
Warning: mkdir(): File exists at /var/www/vendor/friendsofsymfony/jsrouting-bundle/Extractor/ExposedRoutesExtractor.php:179)"} []

The issue should be solved in the upstream package (see: FriendsOfSymfony/FOSJsRoutingBundle#434) but we won't be able to use that - the 3.x version is released only for PHP 8, we are using version 2.8.0 and need to use the workaround until we can upgrade.

Tested in ibexa/experience#26