Revert "Remove the Windows GCC driver."

This reverts commit d6cecde585b0980ed8e0050c5a1d315789fb6356.

The patch broke Simon PJ's Windows build, becuase he didn't
have (and should not need) a separate msys2 gcc.

Following an exchange on the ghc-devs list, Tamar wrote

  Oops, sorry, didn’t notice it because both mine and harbormaster’s
  msys2 have separate GCCs installed as well.

  I don’t see an easy fix that would also work for end user Configure
  based cabal installs. So I think I’ll have to go back to the drawing
  board for this one.

  You can just leave it reverted.

1 files changed, 8 insertions, 0 deletions

diff --git a/configure.ac b/configure.ac
index 3c5e17a0fa..c0961cf8fc 100644
--- a/configure.ac
+++ b/configure.ac
@@ -302,6 +302,8 @@ fail() {
 if test "$HostOS" = "mingw32"
 then
     # Find the mingw-w64 7z file to extract.
+    # NB. If you update the tarballs to a new version of gcc, don't
+    # forget to tweak the paths in driver/gcc/gcc.c.
     if test "$HostArch" = "i386"
     then
         mingw_arch="i686"
@@ -364,6 +366,12 @@ set_up_tarballs() {
         mv "inplace/${tarball_mingw_dir}" inplace/mingw &&
         touch inplace/mingw
 
+        # NB. Now since the GCC is hardcoded to use /mingw32 we need to
+        # make a wrapper around it to give it the proper paths
+        mv inplace/mingw/bin/gcc.exe inplace/mingw/bin/realgcc.exe
+        PATH=`pwd`/inplace/mingw/bin:$PATH
+        inplace/mingw/bin/realgcc.exe driver/gcc/gcc.c driver/utils/cwrapper.c driver/utils/getLocation.c -Idriver/utils -o inplace/mingw/bin/gcc.exe
+
         AC_MSG_NOTICE([In-tree MingW-w64 tree created])
     fi
 }