[clang] default clause replaced by otherwise clause for metadirective in OpenMP 5.2 (PR #128640)

[Urvi Rav via cfe-commits]

ravurvi20 wrote:

Previous commit was reverted due to a failing test case, which has been resolved now. Parsing changes have been approved in the previous PR.
[125648](https://github.com/llvm/llvm-project/pull/125648)

https://github.com/llvm/llvm-project/pull/128640