Since the build was switched to meson a couple of years ago gst1-libav
simply uses libffmpeg and the codec configuration previous passed via
CONFIGURE_ARGS is completely ignored. This is misleading as all those
options are still present in menuconfig but don't have any effect.
Remove all dead code from build recipe.
Fixes: de426d431 ("gst1-libav: update to 1.17.1") Signed-off-by: Daniel Golle <redacted>