gitlab-ci: build snap using an Ubuntu 18.04 environment
Build against the ubuntu:18.04 Docker image. As we are not producing any architecture dependent data, we don't need to build with xenial
to produce a snap usable with core
as a base.
Using bionic as a build environment also means we can use the sassc from the archive rather than building our own copy.
Looking over the diffs, the main changes to the resulting snap are:
- updates to the Ambiance/Radiance GTK themes
- updates to the Humanity icon theme
- Raleigh GTK 2 theme is gone (but was never exported)
- Default and Emacs keyboard theme files are gone (but were never exported)
Edited by James Henstridge