Since:

```
commit eb2dae8fd6aea04673fdd5b0fdf05e4e2ce1c2ee
Author: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Date:   Sat Mar 4 11:03:53 2017 -0500

    Rename plugin filesnames to match plugin names

    - libgstgtksink.so -> libgstgtk.so
    - libgstteletextdec.so -> libgstteletex.so
    - libgstcamerabin2.so -> libgstcamerabin.so
    - libgstonvif.so -> libgstrtponvif.so (meson only)
    - sdp -> sdpelem (avoid clash with libgstsdp)
    - gstsiren -> siren
    - libgstkmssink.so -> libgstkms.so

    https://bugzilla.gnome.org/show_bug.cgi?id=779344
```

+ Add hard dependency on the gdkpixbuf plugin as we do require it