Travis uses Ubuntu, which does not ship dnf, so introduce a yum
stage that allows us to test actual generation of trees on Travis.
We use this to generate a tree containing the tools necessary to
create abritrary Fedora-based build images in the future. We base
this on Fedora 27, as that is the last version that is installable
using yum rather than dnf.
In the future, once we support pipelines with nested build-images,
rather than just using the host OS as the build image, this will
allow us to bootstrap arbitrary pipelines on Travis.
Signed-off-by: Tom Gundersen <teg@jklm.no>
Let's always use the latest available Ubuntu release for our CI, we
are interested in potentially building old images, and using old
images as bulid images, but having an old distro as host is not
necessarily an aim. If we want to test with a greater diversity of
distros (which we do), we should do that in VM's, this should just
be for the simple/quick case.
Also restructure a bit to allow for more (named) tests.
Signed-off-by: Tom Gundersen <teg@jklm.no>
