Build system: prevent "warning: overriding commands for target..."
Build system: prevent "warning: overriding commands for target..."

This happened because the dyn way was listed twice in GhcLibWays for
BuildFlavour=perf.

GaloisInc/halvm-ghc,tjakway/ghcjvm,ghc-android/ghc,mettekou/ghc,oldmanmike/ghc,sgillespie/ghc,siddhanathan/ghc,shlevy/ghc,acowley/ghc,AlexanderPankiv/ghc,sdiehl/ghc,olsner/ghc,nkaretnikov/ghc,shlevy/ghc,anton-dessiatov/ghc,ml9951/ghc,mettekou/ghc,da-x/ghc,mfine/ghc,ml9951/ghc,sgillespie/ghc,mfine/ghc,mettekou/ghc,nkaretnikov/ghc,olsner/ghc,gridaphobe/ghc,mfine/ghc,snoyberg/ghc,mcschroeder/ghc,snoyberg/ghc,da-x/ghc,sdiehl/ghc,oldmanmike/ghc,nkaretnikov/ghc,mcschroeder/ghc,vTurbine/ghc,wxwxwwxxx/ghc,ghc-android/ghc,TomMD/ghc,tjakway/ghcjvm,anton-dessiatov/ghc,anton-dessiatov/ghc,tjakway/ghcjvm,anton-dessiatov/ghc,AlexanderPankiv/ghc,da-x/ghc,ezyang/ghc,sgillespie/ghc,urbanslug/ghc,AlexanderPankiv/ghc,acowley/ghc,gridaphobe/ghc,siddhanathan/ghc,mcschroeder/ghc,wxwxwwxxx/ghc,oldmanmike/ghc,TomMD/ghc,wxwxwwxxx/ghc,da-x/ghc,elieux/ghc,vTurbine/ghc,acowley/ghc,AlexanderPankiv/ghc,urbanslug/ghc,elieux/ghc,oldmanmike/ghc,vTurbine/ghc,mfine/ghc,gridaphobe/ghc,anton-dessiatov/ghc,ml9951/ghc,urbanslug/ghc,oldmanmike/ghc,sdiehl/ghc,nkaretnikov/ghc,sdiehl/ghc,siddhanathan/ghc,vikraman/ghc,vikraman/ghc,siddhanathan/ghc,urbanslug/ghc,tjakway/ghcjvm,siddhanathan/ghc,sgillespie/ghc,vikraman/ghc,ml9951/ghc,GaloisInc/halvm-ghc,nkaretnikov/ghc,vikraman/ghc,oldmanmike/ghc,nkaretnikov/ghc,sdiehl/ghc,snoyberg/ghc,nkaretnikov/ghc,tjakway/ghcjvm,mcschroeder/ghc,ml9951/ghc,oldmanmike/ghc,vikraman/ghc,olsner/ghc,elieux/ghc,vTurbine/ghc,mcschroeder/ghc,acowley/ghc,gridaphobe/ghc,mettekou/ghc,elieux/ghc,vikraman/ghc,urbanslug/ghc,vikraman/ghc,olsner/ghc,da-x/ghc,AlexanderPankiv/ghc,AlexanderPankiv/ghc,TomMD/ghc,sdiehl/ghc,ezyang/ghc,GaloisInc/halvm-ghc,elieux/ghc,wxwxwwxxx/ghc,gridaphobe/ghc,mettekou/ghc,mettekou/ghc,sgillespie/ghc,wxwxwwxxx/ghc,shlevy/ghc,ghc-android/ghc,wxwxwwxxx/ghc,GaloisInc/halvm-ghc,olsner/ghc,sgillespie/ghc,GaloisInc/halvm-ghc,mfine/ghc,ml9951/ghc,anton-dessiatov/ghc,snoyberg/ghc,siddhanathan/ghc,olsner/ghc,ml9951/ghc,ezyang/ghc,elieux/ghc,siddhanathan/ghc,TomMD/ghc,ezyang/ghc,ghc-android/ghc,nushio3/ghc,elieux/ghc,shlevy/ghc,vTurbine/ghc,ghc-android/ghc,AlexanderPankiv/ghc,acowley/ghc,gridaphobe/ghc,nushio3/ghc,snoyberg/ghc,mfine/ghc,nushio3/ghc,ghc-android/ghc,tjakway/ghcjvm,mettekou/ghc,TomMD/ghc,ezyang/ghc,tjakway/ghcjvm,gridaphobe/ghc,urbanslug/ghc,ghc-android/ghc,snoyberg/ghc,mcschroeder/ghc,shlevy/ghc,da-x/ghc,TomMD/ghc,olsner/ghc,snoyberg/ghc,ezyang/ghc,acowley/ghc,nushio3/ghc,nushio3/ghc,sgillespie/ghc,shlevy/ghc,ezyang/ghc,mfine/ghc,anton-dessiatov/ghc,TomMD/ghc,nushio3/ghc,wxwxwwxxx/ghc,mcschroeder/ghc,ml9951/ghc,sdiehl/ghc,shlevy/ghc,vTurbine/ghc,vTurbine/ghc,urbanslug/ghc,da-x/ghc,nushio3/ghc,acowley/ghc,GaloisInc/halvm-ghc,GaloisInc/halvm-ghc