Fix warning caused by ReductionTreePass class

Explicitly declare ReductionTreeBase base class in ReductionTreePass copy constructor.

Reviewed By: mehdi_amini

Differential Revision: https://reviews.llvm.org/D85983

mlir/include/mlir/Reducer/ReductionTreePass.h

@@ -47,7 +47,8 @@ public:
   ReductionTreePass(const Tester *test) : test(test) {}
 
   ReductionTreePass(const ReductionTreePass &pass)
-      : root(new ReductionNode(pass.root->getModule().clone(), nullptr)),
+      : ReductionTreeBase<ReductionTreePass<Reducer, mode>>(pass),
+        root(new ReductionNode(pass.root->getModule().clone(), nullptr)),
         test(pass.test) {}
 
   /// Runs the pass instance in the pass pipeline.