forked from CringeStudios/element-desktop

Since Xenial has the oldest glibc (2.23) of all the active distributions, this attempts to construct a build image based on that. The Dockerfile here was built by recursively expanding the `FROM` lines until reaching `buildpack-deps:bionic-curl` and then changing that to `xenial`. Everything else is the same. Part of https://github.com/vector-im/riot-web/issues/13553