x2goclient: fix build with qt 5.11

pkgs/applications/networking/remote/x2goclient/default.nix

@@ -14,7 +14,9 @@ stdenv.mkDerivation rec {
                   qtbase qtsvg qtx11extras qttools phonon ];
   nativeBuildInputs = [ makeWrapper ];
 
-  patchPhase = ''
+  patches = [ ./qt511.patch ];
+
+  postPatch = ''
      substituteInPlace Makefile \
        --replace "SHELL=/bin/bash" "SHELL=$SHELL" \
        --replace "lrelease-qt4" "${qttools.dev}/bin/lrelease" \

pkgs/applications/networking/remote/x2goclient/qt511.patch

@@ -0,0 +1,15 @@
+diff --git a/src/printwidget.cpp b/src/printwidget.cpp
+index 58a8af7..131d340 100644
+--- a/src/printwidget.cpp
++++ b/src/printwidget.cpp
+@@ -23,6 +23,7 @@
+ #include "x2gosettings.h"
+ #include "x2gologdebug.h"
+ #include <QDir>
++#include <QButtonGroup>
+ #ifdef Q_OS_WIN
+ #include "wapi.h"
+ #endif
+-- 
+2.17.1
+