As a noinst_PROGRAMS, the libtool generated for cross-compiling will be
used, which will mess up the linking. Create a all-local target instead.
Also ensure that building uses always a native version of the tool by
specifying a GTK_UPDATE_ICON_CACHE automake variable.
Finally "config.h" has been created to work for the target platform and
causes problem when cross-compiling. So we temporarily generate a basic
config.h which contains only the strict minimum.
Otherwise we fail to link, seeing this:
/usr/bin/ld: gtk3_widget_factory-widget-factory.o: undefined reference
to symbol 'gdk_pixbuf_new_from_resource'
