Only add -fshow-warning-groups for ghc >= 7.11 (#10752)
Only add -fshow-warning-groups for ghc >= 7.11 (#10752)

sdiehl/ghc,sdiehl/ghc,mcschroeder/ghc,vikraman/ghc,snoyberg/ghc,mcschroeder/ghc,vTurbine/ghc,olsner/ghc,oldmanmike/ghc,tjakway/ghcjvm,mcschroeder/ghc,oldmanmike/ghc,mettekou/ghc,mettekou/ghc,mettekou/ghc,sgillespie/ghc,shlevy/ghc,sgillespie/ghc,ezyang/ghc,mcschroeder/ghc,oldmanmike/ghc,vTurbine/ghc,vikraman/ghc,vTurbine/ghc,sgillespie/ghc,tjakway/ghcjvm,vikraman/ghc,vTurbine/ghc,olsner/ghc,sdiehl/ghc,sgillespie/ghc,sgillespie/ghc,ezyang/ghc,shlevy/ghc,snoyberg/ghc,sdiehl/ghc,snoyberg/ghc,snoyberg/ghc,sgillespie/ghc,vikraman/ghc,mcschroeder/ghc,tjakway/ghcjvm,vikraman/ghc,shlevy/ghc,olsner/ghc,shlevy/ghc,oldmanmike/ghc,ezyang/ghc,olsner/ghc,olsner/ghc,olsner/ghc,oldmanmike/ghc,tjakway/ghcjvm,oldmanmike/ghc,vikraman/ghc,sdiehl/ghc,vikraman/ghc,shlevy/ghc,sdiehl/ghc,shlevy/ghc,ezyang/ghc,sdiehl/ghc,oldmanmike/ghc,shlevy/ghc,vTurbine/ghc,snoyberg/ghc,ezyang/ghc,mettekou/ghc,mcschroeder/ghc,ezyang/ghc,mettekou/ghc,mettekou/ghc,olsner/ghc,mettekou/ghc,vTurbine/ghc,tjakway/ghcjvm,sgillespie/ghc,snoyberg/ghc,tjakway/ghcjvm,ezyang/ghc,tjakway/ghcjvm,snoyberg/ghc,mcschroeder/ghc,vTurbine/ghc