WORKDIR handling

[IsNull]

Hi there, thanks for this Dockerfile, it saved me quite some time. 👍

I just used your ffmpeg integration for a base Java image elderbyte/docker-alpine-jdk8-ffmpeg

I have observed that the WORKDIR seems to get inherited by other Dockerfiles, thus I would reset it to the default location by appending...

WORKDIR /

... at the end of your Dockerfile. Otherwise, it may break client Dockerfiles who depend on the standard WORKDIR.