[Demangle] Include <exception> for IWYU

MaskRay · MaskRay · commit 1d133d9e88de · 2023-07-18T22:10:58.000-07:00
The called std::terminate currently gets the declaration transitively
through llvm/Demangle/Utility.h, removing &lt;exception&gt; from Utility.h
would break ItaniumDemangle.cpp.
diff --git a/llvm/lib/Demangle/ItaniumDemangle.cpp b/llvm/lib/Demangle/ItaniumDemangle.cpp
@@ -18,6 +18,7 @@
 #include <cstdio>
 #include <cstdlib>
 #include <cstring>
+#include <exception>
 #include <functional>
 #include <utility>
 
