[llvm] [MachineOutliner][NFC] Refactor (PR #105398)

[Kyungwoo Lee via llvm-commits]

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@@ -684,7 +688,7 @@ void MachineOutliner::findCandidates(
       continue;
     }
 
-    FunctionList.push_back(*OF);
+    FunctionList.push_back(std::make_unique<OutlinedFunction>(*OF));
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kyulee-com wrote:

This isn't quite right, but either case created implicit copy from the local OutlinedFunction instance. Instead, I also make it unique when it's created in `getOutliningCandidateInfo` so that we can simply move it here.

https://github.com/llvm/llvm-project/pull/105398