[llvm] [LLVM][OpenMP] "nowait" clause is valid for "workshare" (PR #88426)

[Kelvin Li via llvm-commits]

kkwli wrote:

As far as I understand, `nowait` is only allowed on the `end workshare` directive in the spec. I have no objection to extend it to have the clause on the `workshare` directive as long as it also allowed on the `end workshare` directive. However, we probably want to add semantic check for having `nowait` on both `workshare` and `end workshare`. How about the `copyprivate` clause on the `single` directive?

https://github.com/llvm/llvm-project/pull/88426