php-cli run produces notice Notice: Undefined index: _ in /prep/wp-tests-config.php because of $SERVER['_']

[grooverdan]

Describe the bug

During running test.php encountered this notice

Notice: Undefined index: _ in /prep/wp-tests-config.php on line 84

(my line numbers might be a bit different due to other changes in the PRs submitted).

To Reproduce

From https://jira.mariadb.org/browse/MDBF-467 (Except using FROM php:7.4-cli as the Dockerfile start due to 8.0+ errors).

Expected behavior

No "Notice"

Additional context

I traced it down to:
https://github.com/WordPress/phpunit-test-runner/blob/master/prepare.php#L99

I assume $_SERVER isn't set during CLI runs.