Build Tools: Change the PHPUnit Docker image's working directory to match the other images.

Also, pass the `WP_MULTISITE` environment variable along to the container.

See #47767.



git-svn-id: https://develop.svn.wordpress.org/trunk@45800 602fd350-edb4-49c9-b593-d223f7449a82

docker-compose.yml

@@ -97,11 +97,12 @@ services:
     environment:
       LOCAL_PHP_XDEBUG: ${LOCAL_PHP_XDEBUG-false}
       LOCAL_PHP_MEMCACHED: ${LOCAL_PHP_MEMCACHED-false}
+      WP_MULTISITE: ${WP_MULTISITE-false}
 
     volumes:
       - ./tools/local-env/phpunit-config.ini:/usr/local/etc/php/conf.d/phpunit-config.ini
-      - ./:/wordpress-develop
-      - phpunit-uploads:/wordpress-develop/${LOCAL_DIR-src}/wp-content/uploads
+      - ./:/var/www
+      - phpunit-uploads:/var/www/${LOCAL_DIR-src}/wp-content/uploads
 
     # The init directive ensures the command runs with a PID > 1, so Ctrl+C works correctly.
     init: true