[Backport to llvm_release_170] Explicitly cast OCLMemOrderKind members from std::memory_order in C++20 case (#3259)

Backport of PR #3254 into `llvm_release_170`.

All commits applied cleanly.

Co-authored-by: Jakub Jakacki <jakub.jakacki@intel.com>

Author: github-actions[bot]

lib/SPIRV/OCLUtil.h

@@ -99,11 +99,11 @@ enum OCLScopeKind {
 // the corresponding constants from 'std::memory_order' enum.
 enum OCLMemOrderKind {
 #if __cplusplus >= 202002L
-  OCLMO_relaxed = std::memory_order_relaxed,
-  OCLMO_acquire = std::memory_order_acquire,
-  OCLMO_release = std::memory_order_release,
-  OCLMO_acq_rel = std::memory_order_acq_rel,
-  OCLMO_seq_cst = std::memory_order_seq_cst
+  OCLMO_relaxed = static_cast<int>(std::memory_order::relaxed),
+  OCLMO_acquire = static_cast<int>(std::memory_order::acquire),
+  OCLMO_release = static_cast<int>(std::memory_order::release),
+  OCLMO_acq_rel = static_cast<int>(std::memory_order::acq_rel),
+  OCLMO_seq_cst = static_cast<int>(std::memory_order::seq_cst)
 #else
   OCLMO_relaxed = std::memory_order::memory_order_relaxed,
   OCLMO_acquire = std::memory_order::memory_order_acquire,