[lib/LTO] Rework optimization remarkers setup.

This makes this code much more similar to what ThinLTO is
using (also API wise), so now we can probably use a single
code path instead of copying stuff around.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@294792 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed