gitlab-ci: Use prebuilt containers

This image has all build dependencies to speed up build and tests. Copied from phosh (World/Phosh/phosh@d8b2e565) with minor modifications for Calls.

Use

.gitlab-ci/run-docker.sh --base debian build --version 0.0.

.gitlab-ci/run-docker.sh --base debian push --version 0.0.

to update.