Not all NetBSD platforms support joysticks. Based on ones which are active
in their GENERIC config's only have those actually compile in NetBSD specific
joystick support. For the rest let the generic joystick support get pulled
in (and then fail to probe so the code will disable it anyways).
Otherwise this fails on any system without <machine/joystick.h>
XXX...This really should be redone at some point since it's messy now and
the original code looks like it had the concept of no joystick support in
the first place.
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