[llvm] [Attributor] Report change when updating ReachesReturn (PR #108965)

[Shilei Tian via llvm-commits]

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@@ -1093,6 +1093,13 @@ struct AAPointerInfoImpl
     return State::numOffsetBins();
   }
   virtual bool reachesReturn() const override { return ReachesReturn; }
+  ChangeStatus setReachesReturn(bool val) {
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shiltian wrote:

```suggestion
  ChangeStatus setReachesReturn(bool Val) {
```

https://github.com/llvm/llvm-project/pull/108965