#5078 MacOS Build fix

Author: akleshchev

indra/newview/llviewerwindow.cpp

@@ -1884,7 +1884,8 @@ LLViewerWindow::LLViewerWindow(const Params& p)
     // pass its value right now. Instead, pass it a nullary function that
     // will, when we later need it, return the value of gKeyboard.
     // boost::lambda::var() constructs such a functor on the fly.
-    mWindowListener = std::make_unique<LLWindowListener>(this, boost::lambda::var(gKeyboard));
+    LLWindowListener::KeyboardGetter getter = [](){ return gKeyboard; };
+    mWindowListener = std::make_unique<LLWindowListener>(this, getter);
     mViewerWindowListener = std::make_unique<LLViewerWindowListener>(this);
 
     mSystemChannel.reset(new LLNotificationChannel("System", "Visible", LLNotificationFilters::includeEverything));