[PHPUnitBridge] Fixed crash on Windows with PHP 8

The install command crashed with the message
"The filename, directory name, or volume label syntax is incorrect.".
It happens only on Windows with PHP 8.

Probably due to https://github.com/php/php-src/blob/PHP-8.0/UPGRADING#L1121-L1123

Author: villfa

bin/simple-phpunit.php

@@ -231,7 +231,7 @@
     }
     $prevRoot = getenv('COMPOSER_ROOT_VERSION');
     putenv("COMPOSER_ROOT_VERSION=$PHPUNIT_VERSION.99");
-    $q = '\\' === \DIRECTORY_SEPARATOR ? '"' : '';
+    $q = '\\' === \DIRECTORY_SEPARATOR && \PHP_VERSION_ID < 80000 ? '"' : '';
     // --no-suggest is not in the list to keep compat with composer 1.0, which is shipped with Ubuntu 16.04LTS
     $exit = proc_close(proc_open("$q$COMPOSER install --no-dev --prefer-dist --no-progress $q", [], $p, getcwd()));
     putenv('COMPOSER_ROOT_VERSION'.(false !== $prevRoot ? '='.$prevRoot : ''));