When debugging LTO issues with ld64, we use -save-temps to save the merged
optimized bitcode file, then invoke ld64 again on the single bitcode file.
The saved bitcode file is already internalized, so we can call
lto_codegen_set_should_internalize and skip running internalization again.
rdar://20227235
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@235211 91177308-0d34-0410-b5e6-96231b3b80d8