[llvm] [NFC][DFAJT] Place `cl::opt`s in the llvm namespace (PR #162212)

[Mircea Trofin via llvm-commits]

mtrofin wrote:

### Merge activity

* **Oct 7, 2:28 PM UTC**: A user started a stack merge that includes this pull request via [Graphite](https://app.graphite.dev/github/pr/llvm/llvm-project/162212).


https://github.com/llvm/llvm-project/pull/162212