test: fix pummel/test-exec

Fix test/pummel/test-exec.js which broke as a result of
e47f972d
(https://github.com/nodejs/node/pull/24951).

(Until very recently, pummel tests were not run at all in CI and
currently only run nightly on master.)

PR-URL: https://github.com/nodejs/node/pull/25677


Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>
Reviewed-By: Daniel Bevenius <daniel.bevenius@gmail.com>
Reviewed-By: Anto Aravinth <anto.aravinth.cse@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>