The sys/oss/gstosssink.c file does not build under NetBSD, rendering 
gst-plugins unbuildable out of the box.  There are basically two problems 
in it: 
 
First, the SNDCTL_DSP_GETODELAY ioctl does not exist in NetBSD.  I'm not 
sure what it's supposed to do, and if it's really needed, but simply 
avoiding its use seem to work fine (it has been patched this way for a 
long time in pkgsrc, with no major problems, AFAICT).  I'm not aware of a 
better solution, though. 
 
Second, there is an ioctl(2) call that has only two arguments.  This is 
wrong, since NetBSD expects three.  All other calls in the file are 
correct, as they pass a null value as the third argument (they use a 
literal 0, though I think they should use NULL).  So the solution is to 
simply add a 0 as the third parameter to that call to make it work.