Use lcov for both Fedora and MSYS2 to create coverage reports and add a second
ci stage which merges the coverage and creates a html report using genhtml.
In the final stage, which is only run on master, the result is published on
gitlab pages.
https://bugzilla.gnome.org/show_bug.cgi?id=795636
The base Fedora image we use for our CI does not always have an updated
Meson package to fit our requirements. Let's install Meson using
Python's pip instead.
We're mostly interested into building and testing everything that gets
pushed to the repository — including merge requests.
When pushing tags, though, we should assume we're spinning a release, so
let's run the dist target, and store the tarball, and the generated
documentation while we're at it, as artifacts on GitLab.
The Dockerfile for the image used for the build is included in tree, and
published on Docker Hub. Using a custom image allows us to avoid the
costly "download and install build dependencies" phase, as well as
controlling the environment a little bit better.
https://bugzilla.gnome.org/show_bug.cgi?id=793635
