[llvm] [LoongArch][NFC] Pre-commit tests for memcmp expansion (PR #166718)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `ppc64le-lld-multistage-test` running on `ppc64le-lld-multistage-test` while building `llvm` at step 12 "build-stage2-unified-tree".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/168/builds/16932

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

```
Step 12 (build-stage2-unified-tree) failure: build (failure) (timed out)
...
1060.268 [129/12/6636] Building CXX object tools/clang/unittests/CMakeFiles/AllClangUnitTests.dir/Tooling/RecursiveASTVisitorTests/CallbacksCallExpr.cpp.o
1075.520 [129/11/6637] Building CXX object lib/Target/AMDGPU/MCTargetDesc/CMakeFiles/LLVMAMDGPUDesc.dir/AMDGPUMCTargetDesc.cpp.o
1075.524 [129/10/6638] Building CXX object tools/clang/unittests/CMakeFiles/AllClangUnitTests.dir/Tooling/RecursiveASTVisitorTests/CallbacksBinaryOperator.cpp.o
1086.406 [129/9/6639] Building CXX object tools/clang/unittests/CMakeFiles/AllClangUnitTests.dir/ASTMatchers/ASTMatchersNodeTest.cpp.o
1089.506 [129/8/6640] Building CXX object lib/Target/AMDGPU/CMakeFiles/LLVMAMDGPUCodeGen.dir/AMDGPUInstructionSelector.cpp.o
1093.900 [129/7/6641] Building CXX object lib/Target/AMDGPU/CMakeFiles/LLVMAMDGPUCodeGen.dir/AMDGPUTargetMachine.cpp.o
1154.705 [129/6/6642] Building CXX object tools/clang/unittests/CMakeFiles/AllClangUnitTests.dir/ASTMatchers/ASTMatchersNarrowingTest.cpp.o
1257.035 [129/5/6643] Building CXX object lib/Target/AMDGPU/AsmParser/CMakeFiles/LLVMAMDGPUAsmParser.dir/AMDGPUAsmParser.cpp.o
1262.865 [129/4/6644] Building CXX object tools/clang/unittests/CMakeFiles/AllClangUnitTests.dir/AST/ASTImporterTest.cpp.o
1526.556 [129/3/6645] Building CXX object tools/clang/unittests/CMakeFiles/AllClangUnitTests.dir/ASTMatchers/ASTMatchersTraversalTest.cpp.o
command timed out: 1200 seconds without output running [b'ninja'], attempting to kill
process killed by signal 9
program finished with exit code -1
elapsedTime=2727.230415

```

</details>

https://github.com/llvm/llvm-project/pull/166718