In some builds, the following object files could be left behind
after make clean:

./libavfilter/metal/utils.o
./libavfilter/metal/vf_yadif_videotoolbox.metallib.o
./libavcodec/x86/h26x/h2656dsp.o
./libavcodec/neon/mpegvideo.o
./ffbuild/bin2c_host.o

Fixes: http://trac.ffmpeg.org/ticket/10895Signed-off-by: Martin Storsjö <martin@martin.st>