[OpenMP] Fix non-determinism in clang task codegen (lastprivates)

[jdoerfert]

LG

clang/lib/CodeGen/CGStmtOpenMP.cpp

for (const Expr *IInit : C->private_copies()) {
         Data.FirstprivateCopies.push_back(IInit);
         Data.FirstprivateInits.push_back(*IElemInitRef);
       }
       ++IRef;
       ++IElemInitRef;
     }
   }
   // Get list of lastprivate variables (for taskloops).
-  llvm::DenseMap<const VarDecl *, const DeclRefExpr *> LastprivateDstsOrigs;
+  llvm::MapVector<const VarDecl *, const DeclRefExpr *> LastprivateDstsOrigs;
   for (const auto *C : S.getClausesOfKind<OMPLastprivateClause>()) {
     auto IRef = C->varlist_begin();
     auto ID = C->destination_exprs().begin();
     for (const Expr *IInit : C->private_copies()) {
       const auto *OrigVD = cast<VarDecl>(cast<DeclRefExpr>(*IRef)->getDecl());
       if (EmittedAsPrivate.insert(OrigVD->getCanonicalDecl()).second) {
         Data.LastprivateVars.push_back(*IRef);
         Data.LastprivateCopies.push_back(IInit);
       }
       LastprivateDstsOrigs.insert(
-          {cast<VarDecl>(cast<DeclRefExpr>(*ID)->getDecl()),
-           cast<DeclRefExpr>(*IRef)});
+          std::make_pair(cast<VarDecl>(cast<DeclRefExpr>(*ID)->getDecl()),
+                         cast<DeclRefExpr>(*IRef)));
       ++IRef;
       ++ID;
     }
   }
   SmallVector<const Expr *, 4> LHSs;
   SmallVector<const Expr *, 4> RHSs;
   for (const auto *C : S.getClausesOfKind<OMPReductionClause>()) {
     Data.ReductionVars.append(C->varlist_begin(), C->varlist_end());