[PHP 8.5] Use PHP_BUILD_DATE constant

PHP 8.5 has a [new constant named `PHP_BUILD_DATE`](https://php.watch/versions/8.5/PHP_BUILD_DATE)
that contains the same value as the `phpinfo` build date.

We currently use "Build date" field parsed from `phpinfo` output, but
on PHP 8.5, we can simply return the `PHP_BUILD_DATE` value.

src/Debug/Utility/Php.php

@@ -36,6 +36,10 @@ class Php
      */
     public function buildDate()
     {
+        if (\defined('PHP_BUILD_DATE')) {
+            return PHP_BUILD_DATE;
+        }
+
         \ob_start();
         \phpinfo(INFO_GENERAL);
         $phpInfo = \ob_get_clean();