pidgin/pidgin

Fix up the dependencies for our gir files and ensure ours will work as a subproject

Testing Done:
Tested against gplugin 0.34.1 and everything is working well.

Reviewed at https://reviews.imfreedom.org/r/942/
if target_machine.system() != 'windows'
CANBERRA = dependency('libcanberra', version: '>= 0.30')
library('notification-sound', 'notification-sound.c',
dependencies : [libpurple_dep, glib, CANBERRA],
name_prefix : '',
install : true, install_dir : PURPLE_PLUGINDIR)
endif