Hopefully fix build on CI

CI noX11 variant fails, complaining HAVE_X11 is not set. I assume this is
because the call to add_definitions is too late. Using config-plasma.h is
cleaner anyway.

src/shell/CMakeLists.txt

@@ -78,9 +78,6 @@ target_link_libraries(plasma-shell
 )
 target_include_directories(plasma-shell PRIVATE "${CMAKE_BINARY_DIR}")
 
-#FIXME: this shouldn't be necessary?
-add_definitions(-DHAVE_X11=${HAVE_X11})
-
 if(HAVE_X11)
   target_link_libraries(plasma-shell ${X11_LIBRARIES} ${XCB_XCB_LIBRARY} )
   target_link_libraries(plasma-shell Qt5::X11Extras)

src/shell/panelview.cpp

@@ -16,6 +16,8 @@
  *  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
  */
 
+#include <config-plasma.h>
+
 #include "panelview.h"
 #include "shellcorona.h"
 #include "panelshadows_p.h"

src/shell/panelview.h

@@ -19,7 +19,6 @@
 #ifndef PANELVIEW_H
 #define PANELVIEW_H
 
-
 #include <view.h>
 #include "panelconfigview.h"
 #include <QtCore/qpointer.h>