[clang] [llvm] [mlir] [OMPIRBuilder] always leave PARALLEL via the same barrier (PR #164586)

[Michael Kruse via cfe-commits]

https://github.com/Meinersbur requested changes to this pull request.

I think the possible reuse of finialization-unrelated code in FinIP.getBlock() should be resolved before landing this PR

https://github.com/llvm/llvm-project/pull/164586