arginfo not regenerated for extension

### Description

On PHP 8.0 arginfo are regenerated when stub is changed

This doesn't work anymore on 8.1

Related to https://github.com/php/php-src/commit/fa9e2b31b88b1189e0b3d29840e3cce9f44c632d

PHP is only set when building php-src, but not for extension


### PHP Version

PHP 8.1

### Operating System

Linux