Add support for Nix

[Kocal]

Before this change, the Symfony CLI was not able to find all PHP versions I installed on my machine through Nix.

With this PR, all my PHP versions are now correctly discovered:

symfony-cli on  main via 🐳 orbstack via 🐹 v1.26.4 took 2s
➜ go build

symfony-cli on  main via 🐳 orbstack via 🐹 v1.26.4
➜ ./symfony-cli local:php:list
+---------+------------------------------------------------------------------------+---------+-------------+-------------+---------+---------+
| Version |                               Directory                                |   PHP   |     PHP     |     PHP     | Server  | System? |
|         |                                                                        |   CLI   |     FPM     |     CGI     |         |         |
+---------+------------------------------------------------------------------------+---------+-------------+-------------+---------+---------+
| 8.1.34  | /nix/store/0b124alj3m71nj2kz4mvh3yph729g45f-php-with-extensions-8.1.34 | bin/php | bin/php-fpm | bin/php-cgi | PHP FPM |         |
| 8.2.31  | /nix/store/h4q20jqavc40gcy8nlxn7r826b15cmy6-php-with-extensions-8.2.31 | bin/php | bin/php-fpm | bin/php-cgi | PHP FPM |         |
| 8.3.31  | /nix/store/xxzf9zv1rv95bjjmbrdkc2hyb3h4lb31-php-with-extensions-8.3.31 | bin/php | bin/php-fpm | bin/php-cgi | PHP FPM |         |
| 8.4.22  | /nix/store/d8wzkxvwhp0vd8aizgrk8aq0cykcsgik-php-with-extensions-8.4.22 | bin/php | bin/php-fpm | bin/php-cgi | PHP FPM | *       |
| 8.5.7   | /nix/store/7grs0mlr1nxjxjmw5iyk3mqpfsr7lwi6-php-with-extensions-8.5.7  | bin/php | bin/php-fpm | bin/php-cgi | PHP FPM |         |
+---------+------------------------------------------------------------------------+---------+-------------+-------------+---------+---------+

[fabpot]

Thank you @Kocal.