platform_decoding: Add ffmpeg wrapper for MD5 comparison.

This binary wraps around ffmpeg shipping with images, outputting the
resulting hashes one per line. This allows us to reuse the same
platform decoding validation the V4L2 and VAAPI binaries use.

BUG=b:225233215
TEST=/usr/local/graphics/ffmpeg_md5sum
--video=/usr/local/videos/crowd_run_256X144_fr15_bd8_8buf_l1.ivf
--flags=-hwaccel --flags=vaapi

Change-Id: I0efb07984785a0cde36e636e54bf55bb9968acbd
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/graphics/+/3586208
Commit-Queue: Jao-ke Chin-Lee <jchinlee@google.com>
Reviewed-by: Ilja Friedel <ihf@chromium.org>
Reviewed-by: Jao-ke Chin-Lee <jchinlee@google.com>
Reviewed-by: Miguel Casas-Sanchez <mcasas@chromium.org>
Tested-by: Jao-ke Chin-Lee <jchinlee@google.com>
3 files changed