test: allow adding known-globals through ENV

PR-URL: https://github.com/nodejs/node/pull/15187
Refs: https://youtrack.jetbrains.com/issue/WEB-27528


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Timothy Gu <timothygu99@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>