[clang] [llvm] [openmp] [offload][OpenMP] Re-enable strict modifier for num_threads (PR #163565)

[Robert Imschweiler via cfe-commits]

ro-i wrote:

Just crashing the program does not seem very user-friendly to me, tbh. The user / dev would then need to debug to check why the program crashed. They could just debug the number of threads without the strict thing if they have to debug anyway.

https://github.com/llvm/llvm-project/pull/163565