[clang] [clang][OpenMP] Fix/enforce order-concurrent-nestable rules (PR #135463)

[Ernesto Su via cfe-commits]

================
@@ -16373,21 +16359,20 @@ OMPClause *SemaOpenMP::ActOnOpenMPOrderClause(
         << getOpenMPClauseName(OMPC_order);
     return nullptr;
   }
-  if (getLangOpts().OpenMP >= 51) {
----------------
ErnestoSu wrote:

Original implementation did not call `setRegionHasOrderConcurrent(true)` for OpenMP 5.0, causing Clang to ignore all order-concurrent nestable rules for `-fopenmp-version=50`.

https://github.com/llvm/llvm-project/pull/135463