Qt5Multimedia includes support for pulseaudio if it detects libpulse
and libpulse-mainloop-glib in the system at build-time. We need to
depend on pulseaudio and libglib2 if it is selected.

Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>
Reviewed-by: Peter Seiderer <ps.report@gmx.net>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>