Fix path to the new build system, now called Hadrian.
Fix path to the new build system, now called Hadrian.

Summary:
The new Shake-based build system has been given a name -- Hadrian,
and now lives in /hadrian directory.

This fixes the path to the configuration file to be populated by
the configure script.

Test Plan: Run Hadrian build.

Reviewers: thomie, bgamari, hvr, austin

Reviewed By: austin

Subscribers: erikd

Differential Revision: https://phabricator.haskell.org/D2153

mettekou/ghc,olsner/ghc,sdiehl/ghc,snoyberg/ghc,olsner/ghc,shlevy/ghc,snoyberg/ghc,mettekou/ghc,olsner/ghc,snoyberg/ghc,sdiehl/ghc,vikraman/ghc,ezyang/ghc,vTurbine/ghc,sdiehl/ghc,vTurbine/ghc,shlevy/ghc,shlevy/ghc,shlevy/ghc,mettekou/ghc,vTurbine/ghc,olsner/ghc,olsner/ghc,sdiehl/ghc,shlevy/ghc,mettekou/ghc,mettekou/ghc,ezyang/ghc,sgillespie/ghc,vikraman/ghc,vTurbine/ghc,vTurbine/ghc,ezyang/ghc,ezyang/ghc,vikraman/ghc,shlevy/ghc,sdiehl/ghc,sdiehl/ghc,vTurbine/ghc,mettekou/ghc,vikraman/ghc,vikraman/ghc,sgillespie/ghc,vikraman/ghc,ezyang/ghc,snoyberg/ghc,ezyang/ghc,snoyberg/ghc,olsner/ghc,shlevy/ghc,sgillespie/ghc,sgillespie/ghc,snoyberg/ghc,sgillespie/ghc,sdiehl/ghc,snoyberg/ghc,sgillespie/ghc,vTurbine/ghc,ezyang/ghc,mettekou/ghc,vikraman/ghc,olsner/ghc,sgillespie/ghc