[llvm] [AMDGPU][Passes] Invoke CGSCCOptimizerLateEP callbacks in LTO pipeline (PR #203262)

[Shilei Tian via llvm-commits]

shiltian wrote:

> Why do you say CGSCCOptimizerLateEP is only per-TU, as opposed to the other extension points?

That's my speculation based on how it is _currently_ used.

https://github.com/llvm/llvm-project/pull/203262