AppImage should be genarated on a "old" distribution to be sure that
libc versions are compatible.
However, we need at least ubuntu bionic to have QWebEngine packaged.
Let's prepare our AppDir directory in bionic and generate the appimage
in xenial.
By using a small launcher script, we check that libc versions are
compatible and else print a nice message instead of crash.
See https://github.com/probonopd/linuxdeployqt/issues/340
As we mount the kiwix-build (source) directory at run, the docker images
are independent of the source. This will greatly reduce the number of
docker images we have to create.
- Use the same structure than xenial dockerfile.
- Do not try to deploy in the docker image as the deployement is made on
the host.
- Use user `ci_builder` instead of `builder` as it make flatpak fail.
Matthieu Gautier