Allow passing ini settings to PHP

[JeroenVanOort]

I'm pretty sure this would solve the problem explained in https://github.com/nunomaduro/collision/issues/284 . It works with both

php -d pcov.enabled=1 artisan test --coverage -d pcov.enabled=1

and

php -d pcov.enabled=1 artisan test --parallel --coverage -d pcov.enabled=1. I did not try pest, though.

I don't see an easy way to put this under test. Does anyone has an idea for that? Or would it be ok to not have it under test?