Make sure to include config.h, to pickup LLVM_ON_WIN32.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@109721 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Support/CrashRecoveryContext.cpp b/lib/Support/CrashRecoveryContext.cpp
index c079182..1213484 100644
--- a/lib/Support/CrashRecoveryContext.cpp
+++ b/lib/Support/CrashRecoveryContext.cpp
@@ -9,6 +9,7 @@
 
 #include "llvm/Support/CrashRecoveryContext.h"
 #include "llvm/ADT/SmallString.h"
+#include "llvm/Config/config.h"
 #include "llvm/System/ThreadLocal.h"
 #include <setjmp.h>
 #include <cstdio>