[llvm] [AMDGPU] Run LowerLDS at the end of the fullLTO pipeline (PR #75333)

[Matt Arsenault via llvm-commits]

arsenm wrote:

> > Can we get some tests for this? In particular I would like to be sure that we still compile correctly -O0 + LTO. Do we have tests that run the module lowering multiple times?
> 
> #81729 added one

That only covers the second part, not the pipeline change 

https://github.com/llvm/llvm-project/pull/75333