[clang] [llvm] Introduce -defer-thinlto-prelink-coro-split that skips Coro passes in ThinLTO pre-link pipeline (PR #107153)

[Wei Wang via cfe-commits]

apolloww wrote:

> What's the scenario in which we do ThinLTO prelink and then go to codegen (i.e. skip thinlto post-link)?

In #104525, one use case is that pre-link output was used directly by `llc`. I think it's hard to control where it's going to be used due to this is a split phase workflow, so guarding it with a flag may be a better approach when user knows what to expect. 

https://github.com/llvm/llvm-project/pull/107153