[MCJIT] Replace JITEventListener::anchor (temporarily removed in r222861), and

move GDBRegistrationListener into ExecutionEngine to avoid layering violation.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@222864 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/ExecutionEngine/JITEventListener.h

@@ -113,6 +113,8 @@ public:
     return nullptr;
   }
 #endif // USE_OPROFILE
+private:
+  virtual void anchor();
 };
 
 } // end namespace llvm.