Temporarily disable ChangeModtimeAndDigest (test AppVeyor speed up).
Temporarily disable ChangeModtimeAndDigest (test AppVeyor speed up).

[skip ci]

sdiehl/ghc,sdiehl/ghc,snowleopard/hadrian,snowleopard/shaking-up-ghc,sdiehl/ghc,bgamari/shaking-up-ghc,sdiehl/ghc,sdiehl/ghc,sdiehl/ghc,izgzhen/hadrian,sdiehl/ghc