Fix gcc wrapper for new mingw binaries

configure.ac

@@ -453,7 +453,11 @@ then
             tar --lzma -xf ../../ghc-tarballs/mingw/w32api*.tar.lzma    &&
             mv bin/gcc.exe bin/realgcc.exe
         )
-        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
+        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
+        if ! test -e inplace/mingw/bin/gcc.exe
+        then
+            AC_MSG_ERROR([GHC is required unless bootstrapping from .hc files.])
+        fi
         AC_MSG_NOTICE([In-tree mingw tree created])
     fi
     if ! test -d inplace/perl ||

driver/gcc/gcc.c

@@ -8,14 +8,40 @@
 #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;
+    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");
+    }
+
     /* 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. */