Implement the equivalent of D4955 (#648)
Implement the equivalent of D4955 (#648)

* implement the equivalent of D4991 for hadrian

* use stage2 instead of stage == Stage2

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