[llvm] [CodeGen] MachineVerifier to check early-clobber constraint (PR #151421)

[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/41946

<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 :: Transforms/stack-arrays.f90 (3960 of 3969)
PASS: Flang :: Driver/mcmodel.f90 (3961 of 3969)
PASS: Flang :: Driver/use-module-error.f90 (3962 of 3969)
PASS: flang-OldUnit :: Evaluate/real.test (3963 of 3969)
PASS: Flang :: Driver/use-module.f90 (3964 of 3969)
PASS: Flang :: Driver/fopenmp.f90 (3965 of 3969)
PASS: Flang :: Driver/omp-driver-offload.f90 (3966 of 3969)
PASS: Flang :: Driver/linker-options.f90 (3967 of 3969)
PASS: flang-Unit :: Optimizer/./FlangOptimizerTests/147/150 (3968 of 3969)
PASS: Flang :: Intrinsics/math-codegen.fir (3969 of 3969)
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=2042.823861

```

</details>

https://github.com/llvm/llvm-project/pull/151421