Add missing include.

llvm-svn: 230910
diff --git a/clang/lib/Driver/Tools.cpp b/clang/lib/Driver/Tools.cpp
index b0e581b..de3d5a6 100644
--- a/clang/lib/Driver/Tools.cpp
+++ b/clang/lib/Driver/Tools.cpp
@@ -24,6 +24,7 @@
 #include "clang/Driver/SanitizerArgs.h"
 #include "clang/Driver/ToolChain.h"
 #include "clang/Driver/Util.h"
+#include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/ADT/StringSwitch.h"