gstreamer1.0-libav: Transition to meson based builds
meson based builds exclusively rely on external FFmpeg builds. The internal
copy was added at a time when stable FFmpeg releases did not exist. They
do nowadays, so the internal copy is not needed anymore. As a result, large
portions of the recipe are unnecessary, since they set up the internal
copy. Same goes for the patches and the zlib/bzip2/xz dependendencies.
Signed-off-by: Carlos Rafael Giani <crg7475@mailbox.org> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
