[llvm] [AMDGPU] Make sort ordering in `AMDGPURewriteAGPRCopyMFMAImpl::eliminateSpillsOfReassignedVGPRs()` strict weak. (PR #162493)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `ppc64le-flang-rhel-clang` running on `ppc64le-flang-rhel-test` while building `llvm` at step 6 "test-build-unified-tree-check-flang".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/157/builds/41600

<details>
<summary>Here is the relevant piece of the build log for the reference</summary>

```
Step 6 (test-build-unified-tree-check-flang) failure: 1200 seconds without output running [b'ninja', b'check-flang'], attempting to kill
...
PASS: Flang :: Semantics/structconst01.f90 (3869 of 3879)
PASS: Flang :: Semantics/typed-subr.f90 (3870 of 3879)
PASS: Flang :: Semantics/ucobound.f90 (3871 of 3879)
PASS: Flang :: Semantics/undef-result01.f90 (3872 of 3879)
XFAIL: Flang :: Semantics/unlockstmt02.f90 (3873 of 3879)
PASS: Flang :: Semantics/unlockstmt01.f90 (3874 of 3879)
PASS: Flang :: Semantics/symbol17.f90 (3875 of 3879)
PASS: Flang :: Transforms/stack-arrays.f90 (3876 of 3879)
PASS: Flang :: Transforms/tbaa-local-alloc-threshold.fir (3877 of 3879)
PASS: Flang :: Intrinsics/math-codegen.fir (3878 of 3879)
command timed out: 1200 seconds without output running [b'ninja', b'check-flang'], attempting to kill
process killed by signal 9
program finished with exit code -1
elapsedTime=4508.125170

```

</details>

https://github.com/llvm/llvm-project/pull/162493