[MBFI] Move BranchFolding::MBFIWrapper to its own files. NFC.

Summary:
To avoid header file circular dependency issues in passing updated MBFI (in
MBFIWrapper) to the interface of profile guided size optimizations.

A prep step for (and split off of) D73381.

Reviewers: davidxl

Subscribers: mgorny, hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D73494
diff --git a/llvm/lib/CodeGen/CMakeLists.txt b/llvm/lib/CodeGen/CMakeLists.txt
index 470b027..0a299da 100644
--- a/llvm/lib/CodeGen/CMakeLists.txt
+++ b/llvm/lib/CodeGen/CMakeLists.txt
@@ -99,6 +99,7 @@
   MachineVerifier.cpp
   ModuloSchedule.cpp
   PatchableFunction.cpp
+  MBFIWrapper.cpp
   MIRPrinter.cpp
   MIRPrintingPass.cpp
   MacroFusion.cpp