[NFC][ThinLTO] Avoid temporary std::string (#130353)

Preparation for CFI Index refactoring,
which will fix O(N^2) in ThinLTO indexing.

Author: vitalybuka

llvm/lib/Transforms/IPO/LowerTypeTests.cpp

@@ -1699,9 +1699,9 @@ void LowerTypeTestsModule::buildBitSetsFromFunctionsNative(
 
       if (IsExported) {
         if (IsJumpTableCanonical)
-          ExportSummary->cfiFunctionDefs().insert(std::string(F->getName()));
+          ExportSummary->cfiFunctionDefs().emplace(F->getName());
         else
-          ExportSummary->cfiFunctionDecls().insert(std::string(F->getName()));
+          ExportSummary->cfiFunctionDecls().emplace(F->getName());
       }
 
       if (!IsJumpTableCanonical) {