[ORC] Pass FailedSNs by const-ref. NFCI. (#169600)

Avoids a vector copy.

Author: lhames

llvm/include/llvm/ExecutionEngine/Orc/WaitingOnGraph.h

@@ -592,7 +592,7 @@ template <typename ContainerIdT, typename ElementIdT> class WaitingOnGraph {
                             std::vector<std::unique_ptr<SuperNode>> &Failed,
                             SuperNodeDepsMap &SuperNodeDeps,
                             ElemToSuperNodeMap &ElemToSNs,
-                            std::vector<SuperNode *> FailedSNs) {
+                            const std::vector<SuperNode *> &FailedSNs) {
     for (size_t I = 0; I != SNs.size();) {
       auto &SN = SNs[I];