multimedia/pipewire: unbreak GSTREAMER=off after 1821334ec43b
meson.build:329:6: ERROR: Problem encountered: gstreamer-device-provider is enabled but glib-2.0 was not found.
PR: 270725
Reported by: mord0d@firemail.cc
(cherry picked from commit 6744d5e122dfe12d2fba9710d84d38d941748302)