xsfbs.mk: more parallel make fixing
xsfbs.mk: more parallel make fixing

RsrchBoy/xserver-xorg-input-synaptics,philipn/xserver-xorg-input-synaptics,philipn/xserver-xorg-input-synaptics,facboy/xserver-xorg-video-qxl,facboy/xserver-xorg-video-qxl,philipn/xserver-xorg-input-synaptics,RsrchBoy/xserver-xorg-input-synaptics,facboy/xserver-xorg-video-qxl,facboy/xserver-xorg-video-qxl