give back for ffmpeg on ppc64

[Mathieu Malaterre]

It looks like ffmpeg fails to build on ppc64 due to a timeout:

https://buildd.debian.org/status/fetch.php?pkg=ffmpeg&arch=ppc64&ver=7%3A3.0.2-4&stamp=1465651053

gb ffmpeg_7:3.0.2-4 . ppc64

comments ?