Add a virtual dtor to Delegate to silence -Wnon-virtual-dtor

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@127311 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/LiveRangeEdit.h b/lib/CodeGen/LiveRangeEdit.h
index db62eaa..aa86740 100644
--- a/lib/CodeGen/LiveRangeEdit.h
+++ b/lib/CodeGen/LiveRangeEdit.h
@@ -34,6 +34,7 @@
   struct Delegate {
     /// Called immediately before erasing a dead machine instruction.
     virtual void LRE_WillEraseInstruction(MachineInstr *MI) {}
+    virtual ~Delegate() {}
   };
 
 private: