Adds an ubuntu20 base image, updates the scripts to build against it by default, and updates the pipeline to reference its images. The actual production images have already been built from this branch.
Note that Ubuntu 20.04 includes libssl 1.1 dev, which is incompatible with Rubies prior to 2.4.0. Hence, we provide an additional ubuntu20 base image that includes the legacy libssl1.0-dev packages instead, for building older Rubies. The runtime base image includes both libssl1.0 and libssl1.1 binary packages.
Adds an ubuntu20 base image, updates the scripts to build against it by default, and updates the pipeline to reference its images. The actual production images have already been built from this branch.
Note that Ubuntu 20.04 includes libssl 1.1 dev, which is incompatible with Rubies prior to 2.4.0. Hence, we provide an additional ubuntu20 base image that includes the legacy libssl1.0-dev packages instead, for building older Rubies. The runtime base image includes both libssl1.0 and libssl1.1 binary packages.
Fixes #195