Summary:
D23695665 (https://github.com/facebook/folly/commit/5c3b9d59a815b94df1afed0b7e0050bb75e09178) calls functions defined by this module,
but doesn't ensure that it has been imported.

I believe this to be the reason behind this build failure:

https://github.com/facebook/watchman/pull/856/checks?check_run_id=1135919864#step:52:217

Reviewed By: chadaustin

Differential Revision: D23794292

fbshipit-source-id: 897cfac862fda7420d1c53b0976492231b53dcf8