Right now, Phab's buildbot complains about

  Unexpected failures:
    perf/compiler T1969 [stat too good] (normal)
    perf/compiler T4801 [stat not good enough] (normal)

However, on my workstation, those tests don't fail (c.f. P14).
So this commit tries to blindly tweak those numbers and see if
if Phabricator succeeds to build this code-revision...

Test Plan: Let Harbormaster build it

Reviewers: austin

Subscribers: simonmar, ezyang, carter

Differential Revision: https://phabricator.haskell.org/D210