build: Fix compilation warnings/errors with clang-700.0.72 (apple LLVM 7.0.0)

Change-Id: Iedbebae03740a5d779c84e78d22b74dd9b9009f7
Refs: #3209
diff --git a/daemon/face/unix-stream-factory.hpp b/daemon/face/unix-stream-factory.hpp
index ecb679b..61ef3de 100644
--- a/daemon/face/unix-stream-factory.hpp
+++ b/daemon/face/unix-stream-factory.hpp
@@ -66,7 +66,7 @@
              const FaceConnectFailedCallback& onConnectFailed) DECL_OVERRIDE;
 
   virtual std::list<shared_ptr<const Channel> >
-  getChannels() const;
+  getChannels() const DECL_OVERRIDE;
 
 private:
   /**