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

[Pierre van Houtryve via llvm-commits]

Pierre-vh 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

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