x11-themes/gtk-arc-themes: Speed up build
The build is insanely slow. Inkscape tries to connect to 127.0.0.1:9090
(probably gtk3's broadway backend) which has to timeout first until
the next inkscape call. If this would only happen a couple of times
it would be ok but it happens >500 times. Disable all GDK backends
to prevent that.
Unable to init server: Could not connect to 127.0.0.1: Connection refused