build: add exception header (#5112)

This file uses std::current_exception, so it should
include <exception>

lib/IR/Value.cpp

@@ -33,6 +33,7 @@
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/ManagedStatic.h"
 #include "llvm/Support/raw_ostream.h"
+#include <exception> // HLSL Change - add header.
 #include <algorithm>
 using namespace llvm;