Consider building with pipewire support

Hi Gianfranco,

Oh my, yes, it seems I forgot to add the new pipewire -dev package to the
fluidsynth -dev package.  'not sure how that happened, but my mistake!
Isn't only waiting 48h a bit rushed for an NMU though?  I can of course
import your fix and upload in the next 48h, and I'd like to improve your
changelog entry, because I think you'll agree that the concept of "runtime"
doesn't make sense for headers ;)  If this is truly 0-day urgent, I'm
confident a team member (IIRC Josch is a multimedia-team member) will
upload.

Cheers,
Nicholas

('hope this isn't HTML email, since I'm currently AFK on a phone)