openh264: Fix static build
openh264: Fix static build

This avoids dynamically linking on gnustl, by setting the libgnustl.la
in libopenh264.la's dependency_libs.

https://bugzilla.gnome.org/show_bug.cgi?id=745047

ramaxlo/cerbero,nirbheek/cerbero,multipath-rtp/cerbero,freedesktop-unofficial-mirror/gstreamer__sdk__cerbero,shoreflyer/cerbero,sdroege/cerbero,atsushieno/cerbero,lubosz/cerbero,OptoFidelity/cerbero,superdump/cerbero,OptoFidelity/cerbero,superdump/cerbero,centricular/cerbero,nzjrs/cerbero,nzjrs/cerbero,justinjoy/cerbero,EricssonResearch/cerbero,AlertMe/cerbero,justinjoy/cerbero,atsushieno/cerbero,AlertMe/cerbero,fluendo/cerbero,nzjrs/cerbero,EricssonResearch/cerbero,GStreamer/cerbero,ramaxlo/cerbero,ramaxlo/cerbero,ford-prefect/cerbero,EricssonResearch/cerbero,justinjoy/cerbero,fluendo/cerbero,jackjansen/cerbero,GStreamer/cerbero,ramaxlo/cerbero,EricssonResearch/cerbero,ramaxlo/cerbero,nirbheek/cerbero-old,ikonst/cerbero,justinjoy/cerbero,nirbheek/cerbero,sdroege/cerbero,fluendo/cerbero,fluendo/cerbero,OptoFidelity/cerbero,nzjrs/cerbero,centricular/cerbero,freedesktop-unofficial-mirror/gstreamer__sdk__cerbero,flexVDI/cerbero,OptoFidelity/cerbero,superdump/cerbero,multipath-rtp/cerbero,ford-prefect/cerbero,freedesktop-unofficial-mirror/gstreamer__sdk__cerbero,lubosz/cerbero,nzjrs/cerbero,centricular/cerbero,freedesktop-unofficial-mirror/gstreamer__sdk__cerbero,atsushieno/cerbero,ikonst/cerbero,sdroege/cerbero,multipath-rtp/cerbero,atsushieno/cerbero,freedesktop-unofficial-mirror/gstreamer__cerbero,ford-prefect/cerbero,centricular/cerbero,jackjansen/cerbero,AlertMe/cerbero,sdroege/cerbero,nirbheek/cerbero-old,nirbheek/cerbero-old,ford-prefect/cerbero,shoreflyer/cerbero,atsushieno/cerbero,nirbheek/cerbero-old,AlertMe/cerbero,GStreamer/cerbero,lubosz/cerbero,AlertMe/cerbero,ikonst/cerbero,ikonst/cerbero,EricssonResearch/cerbero,freedesktop-unofficial-mirror/gstreamer__cerbero,shoreflyer/cerbero,superdump/cerbero,freedesktop-unofficial-mirror/gstreamer__cerbero,flexVDI/cerbero,shoreflyer/cerbero,centricular/cerbero,fluendo/cerbero,nirbheek/cerbero,multipath-rtp/cerbero,GStreamer/cerbero,GStreamer/cerbero,flexVDI/cerbero,lubosz/cerbero,multipath-rtp/cerbero,ikonst/cerbero,flexVDI/cerbero,sdroege/cerbero,nirbheek/cerbero,flexVDI/cerbero,shoreflyer/cerbero,jackjansen/cerbero,jackjansen/cerbero,freedesktop-unofficial-mirror/gstreamer__cerbero