[NFC] Add missing includes for LLVM_ENABLE_MODULES builds

[zero9178]

Summary

Building LLVM with the LLVM_ENABLE_MODULES cmake option fails when the modules are being compiled due to missing includes. This is a side effect of some transitive includes that changed recently.

[nikic]

LGTM, thanks!

[vsapsai]

Thank you for fixing this, Markus.

llvm/include/llvm/CodeGen/MBFIWrapper.h

 // tail-merged blocks. Used by the TailDuplication and MachineBlockPlacement.
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef LLVM_CODEGEN_MBFIWRAPPER_H
 #define LLVM_CODEGEN_MBFIWRAPPER_H
 
 #include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/Optional.h"
 #include "llvm/Support/BlockFrequency.h"
 
 namespace llvm {
 
 class MachineBasicBlock;
 class MachineBlockFrequencyInfo;
 
 class MBFIWrapper {

llvm/include/llvm/Support/CFGUpdate.h

 //===- CFGUpdate.h - Encode a CFG Edge Update. ------------------*- C++ -*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
 // This file defines a CFG Edge Update: Insert or Delete, and two Nodes as the
 // Edge ends.
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef LLVM_SUPPORT_CFGUPDATE_H
 #define LLVM_SUPPORT_CFGUPDATE_H
 
+#include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/PointerIntPair.h"
 #include "llvm/Support/Compiler.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/raw_ostream.h"
 
 namespace llvm {
 namespace cfg {