In my build environment, I am behind an HTTP proxy with SSL bump. This means that, when building snaps, I need to be able to configure the system certificate authority with my HTTP proxy's certificate and I need to be able to configure the `http_proxy`, `https_proxy`, and `no_proxy` environment variables. I am also building the snap inside a Vagrant VM that cannot support Multipass. This is a feature request asking for a way to provide HTTP proxy and certificate authority information to snapcraft when building with LXD. I have documented how I worked around this by using Docker in a forum topic: https://forum.snapcraft.io/t/how-to-build-a-snap-behind-a-proxy-with-ssl-bump-in-a-vagrant-vm/14975?u=zicklag.