This makes the bazel image more similar to the bash build, which uses
the image from the docker registry.

mkfifo is used by e.g. kops to send logs to both a /var/log file and to
stdout (which is then captured by docker).

We create a symlink to hostname, to force creation of the /tmp
directory.  There doesn't seem to be a direct way of creating a
directory in the docker_build task in bazel.