Allow `JX` to be redefined for NodeJS files

Summary: This silences a bunch of JSHint warnings.

Test Plan: `arc lint -- support/aphlict/server/lib/AphlictLog.js`

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: Korvin, epriestley

Differential Revision: https://secure.phabricator.com/D11084