[llvm] [SPIRV] Error in backend for vararg functions (PR #169111)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `ppc64le-mlir-rhel-clang` running on `ppc64le-mlir-rhel-test` while building `llvm` at step 5 "build-check-mlir-build-only".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/129/builds/33846

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

```
Step 5 (build-check-mlir-build-only) failure: build (failure) (timed out)
...
728.822 [59/243/4200] Linking CXX static library lib/libMLIRTestPDLL.a
728.881 [59/242/4201] Linking CXX static library lib/libMLIRTestIRDLToCppDialect.a
728.881 [59/241/4202] Linking CXX static library lib/libMLIRTestIR.a
729.023 [59/240/4203] Linking CXX static library lib/libMLIRTestTransforms.a
729.074 [59/239/4204] Linking CXX static library lib/libMLIRGPUToSPIRV.a
729.693 [59/238/4205] Linking CXX executable tools/mlir/unittests/Dialect/ArmSME/MLIRArmSMETests
731.298 [59/237/4206] Linking CXX executable tools/mlir/unittests/Parser/MLIRParserTests
731.628 [59/236/4207] Linking CXX executable tools/mlir/unittests/TableGen/MLIRTableGenTests
732.392 [59/235/4208] Linking CXX executable tools/mlir/unittests/IR/MLIRIRTests
754.601 [59/234/4209] Linking CXX executable tools/mlir/unittests/Dialect/AMDGPU/MLIRAMDGPUTests
command timed out: 1200 seconds without output running [b'ninja', b'check-mlir-build-only'], attempting to kill
process killed by signal 9
program finished with exit code -1
elapsedTime=1955.547006

```

</details>

https://github.com/llvm/llvm-project/pull/169111