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

[Pierre van Houtryve via llvm-commits]

Pierre-vh wrote:

This is causing `LLVM ERROR: Module cannot mix absolute and non-absolute LDS GVs` on the openmp buildbot, and I have no idea why: https://lab.llvm.org/buildbot/#/builders/193/builds/48532/steps/6/logs/FAIL__libomptarget____amdgcn-amd-amdhsa__cuda_no_d
I cannot reproduce it locally either

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