Update Windows GCC driver.
Update Windows GCC driver.

Test Plan: None really, as none of our tests cover this usage. Probably
should add one..

Reviewers: austin, bgamari

Reviewed By: bgamari

Subscribers: thomie, #ghc_windows_task_force

Differential Revision: https://phabricator.haskell.org/D2810

GHC Trac Issues: #12871

olsner/ghc,sdiehl/ghc,shlevy/ghc,sdiehl/ghc,sdiehl/ghc,sdiehl/ghc,shlevy/ghc,sdiehl/ghc,shlevy/ghc,olsner/ghc,ezyang/ghc,shlevy/ghc,ezyang/ghc,ezyang/ghc,olsner/ghc,sdiehl/ghc,shlevy/ghc,sdiehl/ghc,olsner/ghc,ezyang/ghc,ezyang/ghc,olsner/ghc,olsner/ghc,shlevy/ghc,ezyang/ghc,ezyang/ghc,shlevy/ghc,olsner/ghc