Add Shake configuration to configure.ac
Add Shake configuration to configure.ac

The Shake build system requires that this file be generated by autoconf.
Generate it if we find a shake tree.

Reviewers: austin, hvr

Reviewed By: hvr

Subscribers: thomie, erikd

Differential Revision: https://phabricator.haskell.org/D1638

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