Add possibility to declare proxy as build-arg to docker build

[allamand]

Feature Request

We have specific Dockerfile which need to access package through a proxy.
with the old docker_build.sh script I was able to add --build-arg https_proxy=$https_proxy --build-arg http_proxy=$http_proxy to the script to activate the proxy is the var exists.

I would like that operator-sdk build command can pass thoses build-args if http_proxy env var exists.

[joelanford]

@allamand Are you able to make use of the feature in Docker 17.07+ to set proxy variables in ~/.docker/config.json (https://docs.docker.com/network/proxy/)?

[joelanford]

@allamand - Just following up to see if you were able to solve this issue with ~/.docker/config.json, or if there's still a feature you'd like to be added to the SDK?

[allamand]

hi @joelanford, thanks for checking on. In fact I used to build the same code either behind a proxy or with direct access, and if I change the config.json, I need to restart docker which can takes some time. At this time I keep going on with the old docker_build.sh script on which I add the build-args which are enabled only if my $https_proxy is set, so I think that would be great to have operator-sdk build check on this environment variable too.