Fix broken build-system when libffi uses install-sh
Fix broken build-system when libffi uses install-sh

Reviewers: austin, bgamari

Reviewed By: bgamari

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D1494

GHC Trac Issues: #11109

GaloisInc/halvm-ghc,sgillespie/ghc,snoyberg/ghc,GaloisInc/halvm-ghc,tjakway/ghcjvm,sdiehl/ghc,elieux/ghc,elieux/ghc,mcschroeder/ghc,mettekou/ghc,vikraman/ghc,elieux/ghc,tjakway/ghcjvm,nushio3/ghc,snoyberg/ghc,nushio3/ghc,mettekou/ghc,sdiehl/ghc,tjakway/ghcjvm,sdiehl/ghc,elieux/ghc,vTurbine/ghc,tjakway/ghcjvm,elieux/ghc,mettekou/ghc,vTurbine/ghc,vikraman/ghc,mcschroeder/ghc,vikraman/ghc,shlevy/ghc,GaloisInc/halvm-ghc,ezyang/ghc,oldmanmike/ghc,olsner/ghc,gridaphobe/ghc,olsner/ghc,gridaphobe/ghc,elieux/ghc,olsner/ghc,shlevy/ghc,GaloisInc/halvm-ghc,ezyang/ghc,mettekou/ghc,olsner/ghc,shlevy/ghc,ezyang/ghc,sgillespie/ghc,shlevy/ghc,sgillespie/ghc,snoyberg/ghc,nushio3/ghc,sdiehl/ghc,mcschroeder/ghc,oldmanmike/ghc,mettekou/ghc,nushio3/ghc,vikraman/ghc,sgillespie/ghc,snoyberg/ghc,elieux/ghc,snoyberg/ghc,snoyberg/ghc,sgillespie/ghc,ezyang/ghc,vTurbine/ghc,gridaphobe/ghc,tjakway/ghcjvm,mcschroeder/ghc,olsner/ghc,GaloisInc/halvm-ghc,nushio3/ghc,GaloisInc/halvm-ghc,gridaphobe/ghc,shlevy/ghc,sdiehl/ghc,mettekou/ghc,ezyang/ghc,mettekou/ghc,tjakway/ghcjvm,vTurbine/ghc,mcschroeder/ghc,sdiehl/ghc,gridaphobe/ghc,snoyberg/ghc,gridaphobe/ghc,olsner/ghc,ezyang/ghc,mcschroeder/ghc,GaloisInc/halvm-ghc,oldmanmike/ghc,vikraman/ghc,vTurbine/ghc,olsner/ghc,vTurbine/ghc,sgillespie/ghc,nushio3/ghc,shlevy/ghc,vikraman/ghc,shlevy/ghc,oldmanmike/ghc,gridaphobe/ghc,nushio3/ghc,tjakway/ghcjvm,ezyang/ghc,oldmanmike/ghc,oldmanmike/ghc,mcschroeder/ghc,vikraman/ghc,oldmanmike/ghc,sgillespie/ghc,sdiehl/ghc,vTurbine/ghc