Should Dockerfile set GEM_HOME?

[sebb]

docker/Dockerfile currently sets [1]:

ENV GEM_HOME="/srv/gems"

However surely /srv/gems is not defined/created until much later?

[1]
https://github.com/apache/whimsy/blob/5a0ef59e789c4cb58379b61391160825f3c89ca3/docker/Dockerfile#L2