[llvm] [llvm] Use llvm::less_first and llvm::less_second (NFC) (PR #136272)

[Kazu Hirata via llvm-commits]

kazutakahirata wrote:

> @kazutakahirata ,
> 
> [llvm-clang-x86_64-expensive-checks-ubuntu](https://lab.llvm.org/buildbot/#/builders/187) builder also has broken with the following failed tests:
> 
> * LLVM::sched-group-barrier-pre-RA.mir
> * LLVM::sched-group-barrier-pipeline-solver.mir
> 
> see more details here: https://lab.llvm.org/buildbot/#/builders/16/builds/17613/steps/6/logs/stdio

Thank you for letting me know!  Reverting to `std::sort` in `llvm/lib/Target/AMDGPU/AMDGPUIGroupLP.cpp` seems to fix the problems.  I'll post a PR shortly.


https://github.com/llvm/llvm-project/pull/136272