[flang] [llvm] [flang][OpenMP] Check for OpenMP 5.0+ for the if clause on "do simd" (PR #151154)

[Tom Eccles via llvm-commits]

https://github.com/tblah commented:

Well spotted. Please could you add a test to make sure the code in the issue does continue to work with OpenMP 5.0

https://github.com/llvm/llvm-project/pull/151154