[clang] [CIR] Add support for compound assignment statements (PR #137740)

[LLVM Continuous Integration via cfe-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `amdgpu-offload-rhel-9-cmake-build-only` running on `rocm-docker-rhel-9` while building `clang` at step 2 "update-annotated-scripts".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/205/builds/7835

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

```
Step 2 (update-annotated-scripts) failure: update (failure)
git version 2.43.5
fatal: unable to access 'https://github.com/llvm/llvm-zorg.git/': Failed to connect to github.com port 443: Connection timed out
fatal: unable to access 'https://github.com/llvm/llvm-zorg.git/': Failed to connect to github.com port 443: Connection timed out

```

</details>

https://github.com/llvm/llvm-project/pull/137740