Fixes [1]:
  /usr/bin/make -j4 -C /home/buildroot/autobuild/run/instance-3/output/build/qt5tools-5.5.1/src/qtdiag
  make[2]: *** No targets specified and no makefile found.  Stop.
[1] http://autobuild.buildroot.net/results/4ee/
4eee2a7cee8fce63b0419668da8bd55b3cfd00af
Signed-off-by: Peter Seiderer <ps.report@gmx.net>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
 
 config BR2_PACKAGE_QT5TOOLS_QTDIAG
        bool "qtdiag"
+       select BR2_PACKAGE_QT5BASE_GUI
        help
          Compile and install the qtdiag program.