build-helper/cmake-wxWidgets-gtk3: set configure_args, too

CMake on their mission to handle all use-cases, ships a FindwxWidgets,
this module ignores WX_CONFIG environment variable,
even the code seems to respect it.

common/build-helper/cmake-wxWidgets-gtk3.sh

@@ -3,3 +3,4 @@ if [ "$CROSS_BUILD" ]; then
 else
 	export WX_CONFIG=/usr/bin/wx-config-gtk3
 fi
+configure_args+=" -DwxWidgets_CONFIG_EXECUTABLE=${WX_CONFIG} "