Add missing include.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@76555 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/MSIL/MSILWriter.h b/lib/Target/MSIL/MSILWriter.h
index 5dab0e8..6c52a17 100644
--- a/lib/Target/MSIL/MSILWriter.h
+++ b/lib/Target/MSIL/MSILWriter.h
@@ -19,6 +19,7 @@
 #include "llvm/IntrinsicInst.h"
 #include "llvm/Pass.h"
 #include "llvm/PassManager.h"
+#include "llvm/ADT/StringRef.h"
 #include "llvm/Analysis/FindUsedTypes.h"
 #include "llvm/Analysis/LoopInfo.h"
 #include "llvm/Support/FormattedStream.h"