[flang] [llvm] [Flang] [OpenMP] Add semantic checks for detach clause in task (PR #119172)

[Krzysztof Parzyszek via llvm-commits]

https://github.com/kparzysz approved this pull request.

Sorry for the delay in reviewing.  Looks ok to me, but please wait for @tblah's input as well.

https://github.com/llvm/llvm-project/pull/119172