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, 66 insertions, 0 deletions

diff --git a/driver/gcc/gcc.c b/driver/gcc/gcc.c
new file mode 100644
index 0000000000..b398c5ea46
--- /dev/null
+++ b/driver/gcc/gcc.c
@@ -0,0 +1,66 @@
+
+/* gcc on mingw is hardcoded to use /mingw (which is c:/mingw) to
+   find various files. If this is a different version of mingw to the
+   one that we have in the GHC tree then things can go wrong. We
+   therefore need to add various -B flags to the gcc commandline,
+   so that it uses our in-tree mingw. Hence this wrapper. */
+
+#include "cwrapper.h"
+#include "getLocation.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+
+int main(int argc, char** argv) {
+    char *binDir;
+    char *exePath;
+    char *preArgv[4];
+    char *oldPath;
+    char *newPath;
+    char *base;
+    char *version;
+    int n;
+
+    binDir = getExecutablePath();
+    exePath = mkString("%s/realgcc.exe", binDir);
+
+    /* We need programs like
+           inplace/mingw/libexec/gcc/mingw32/4.5.0/cc1.exe
+       to be able to find the DLLs in inplace/mingw/bin, so we need to
+       add it to $PATH */
+    oldPath = getenv("PATH");
+    if (!oldPath) {
+        die("Couldn't read PATH\n");
+    }
+    n = snprintf(NULL, 0, "PATH=%s;%s", binDir, oldPath);
+    n++;
+    newPath = malloc(n);
+    if (!newPath) {
+        die("Couldn't allocate space for PATH\n");
+    }
+    snprintf(newPath, n, "PATH=%s;%s", binDir, oldPath);
+    n = putenv(newPath);
+    if (n) {
+        die("putenv failed\n");
+    }
+
+    /* GCC Version. */
+    version = mkString("%d.%d.%d", __GNUC__, __GNUC_MINOR__, __GNUC_PATCHLEVEL__);
+
+    /* Without these -B args, gcc will still work. However, if you
+       have a mingw installation in c:/mingw then it will use files
+       from that in preference to the in-tree files. */
+    preArgv[0] = mkString("-B%s", binDir);
+    preArgv[1] = mkString("-B%s/../lib", binDir);
+#if defined(__MINGW64__)
+    base = mkString("x86_64-w64-mingw32");
+#else
+    base = mkString("i686-w64-mingw32");
+#endif
+
+    preArgv[2] = mkString("-B%s/../lib/gcc/%s/%s"    , binDir, base, version);
+    preArgv[3] = mkString("-B%s/../libexec/gcc/%s/%s", binDir, base, version);
+
+    run(exePath, 4, preArgv, argc - 1, argv + 1);
+}
+