Make StringRef to std::string conversions explicit.

Author: varungandhi-apple

lib/Serialization/ModuleFileCoreTableInfo.h

@@ -457,7 +457,7 @@ class ModuleFileSharedCore::DerivativeFunctionConfigTableInfo {
       int32_t nameLength = endian::readNext<int32_t, little, unaligned>(data);
       StringRef mangledName(reinterpret_cast<const char *>(data), nameLength);
       data += nameLength;
-      result.push_back({mangledName, genSigId});
+      result.push_back({std::string(mangledName), genSigId});
     }
     return result;
   }

lib/Serialization/Serialization.cpp

@@ -5154,7 +5154,8 @@ void Serializer::writeAST(ModuleOrSourceFile DC) {
       for (auto config : entry.second) {
         std::string paramIndices = config.first.str().str();
         auto genSigID = addGenericSignatureRef(config.second);
-        derivativeConfigs[entry.first].push_back({paramIndices, genSigID});
+        derivativeConfigs[entry.first].push_back(
+          {std::string(paramIndices), genSigID});
       }
     }
     index_block::DerivativeFunctionConfigTableLayout DerivativeConfigTable(Out);