Add missing gthread-2.0 dependency

[Vild]

Fixes the 'undefined symbol: g_thread_init' error when running programs that link to glibd.

Reason:

To use g_thread_init() in your program, you have to link with the libraries that the command pkg-config —libs gthread-2.0 outputs.

• https://docs.gtk.org/glib/type_func.Thread.init.html

[MikeWey]

Thanks.