this is part of this commit  https://github.com/romainneutron/symfony/commit/923fc5873ac65011c14c397383cded4e6cdc96d7

On my computer, zombie processes might have remain in case of unit test failure.
It happend that some infinite loops were running and slowing down my system. A `ps` call alerted me that many (~100) `php -r "while (true) {}"` were running after half an hour debugging things. 

I propose to change these. As tests pass and nothing changed in the way we test things, I think it's a better idea to have these commands instead of the infinite loops for symfony/process developers.