[ExecutionEngine] Avoid repeated hash lookups (NFC) (llvm#127303)

Author: kazutakahirata

llvm/lib/ExecutionEngine/Orc/MachOPlatform.cpp

@@ -635,11 +635,12 @@ void MachOPlatform::pushInitializersLoop(
       Worklist.pop_back();
 
       // If we've already visited this JITDylib on this iteration then continue.
-      if (JDDepMap.count(DepJD))
+      auto [It, Inserted] = JDDepMap.try_emplace(DepJD);
+      if (!Inserted)
         continue;
 
       // Add dep info.
-      auto &DM = JDDepMap[DepJD];
+      auto &DM = It->second;
       DepJD->withLinkOrderDo([&](const JITDylibSearchOrder &O) {
         for (auto &KV : O) {
           if (KV.first == DepJD)