[clang] [clang] Increase VecLib bitfield size to 4 bits in CodeGenOptions.def (PR #108804)

[LLVM Continuous Integration via cfe-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `openmp-offload-sles-build-only` running on `rocm-worker-hw-04-sles` while building `clang` at step 4 "configure-openmp".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/140/builds/6859

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

```
Step 4 (configure-openmp) failure: cmake (failure)

```

</details>

https://github.com/llvm/llvm-project/pull/108804