Introduce Glib's GIO library as a dependency in the client

Acceptance criteria:

• Introduce Glib's GIO dbus library (libgio-2.0.so, search for D-Bus on that page to find various sub categories) as a library dependency in the client.
• Link to one symbol to force the dependency (easy way is just to create a pointer to an API function, it doesn't need to be used).
• It must be possible to completely compile out the Glib dependency, and hence the API. Use a similar approach as the nolzma toggle which already exists.
• Feature branch: feature-client_auth_api