Simplify LTOInternalize into UpdateLLVMCompilerUsed

It is now only doing the update to the llvm.compiler_used global.
The client has to call separately the internalization stage.
Hopefully the code is simpler to understand this way.

From: Mehdi Amini <mehdi.amini@apple.com>
llvm-svn: 266174
diff --git a/llvm/lib/LTO/CMakeLists.txt b/llvm/lib/LTO/CMakeLists.txt
index 6c8dcc6..1a592f0 100644
--- a/llvm/lib/LTO/CMakeLists.txt
+++ b/llvm/lib/LTO/CMakeLists.txt
@@ -1,7 +1,7 @@
 add_llvm_library(LLVMLTO
   LTOModule.cpp
   LTOCodeGenerator.cpp
-  LTOInternalize.cpp
+  UpdateCompilerUsed.cpp
   ThinLTOCodeGenerator.cpp
 
   ADDITIONAL_HEADER_DIRS