Summary:
There is a problem where harbourmaster builds complain about a bad
boolFormula.stderr

    ghc-api/annotations boolFormula [bad stderr] (normal)

The problem does not occur for a local build on my box

This patch turns off warnings for this test, to get rid of the stderr
issue.

Test Plan: ./validate

Reviewers: hvr, austin

Reviewed By: austin

Subscribers: bgamari, thomie, hvr

Differential Revision: https://phabricator.haskell.org/D888