[NFC] Add some missing header includes

[etcwilde]

Summary

Fixing local build failures due to missing header includes.

[etcwilde]

Grabbed the right patch

[mib]

LGTM!

llvm/include/llvm/Support/Format.h

 #define LLVM_SUPPORT_FORMAT_H
 
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/Support/DataTypes.h"
 #include <cassert>
 #include <cstdio>
+#include <optional>
 #include <tuple>
 #include <utility>
 
 namespace llvm {
 
 /// This is a helper class used for handling formatted output.  It is the
 /// abstract base class of a templated derived class.
 class format_object_base {