GH CD: chechout all projects, even self from prep_sources.yml so that revisions.txt is not too old for Makefile.

revisions.txt is expected in $CWD When building Windows installer, in $CWD/sources for Snap. Deal with it for now.

GH CD: Seriously ? https://github.com/actions/upload-artifact#maintaining-file-permissions-and-case-sensitive-files

GH CD: seems that reusable workflow outputs can't make their way through.

GH CD: place revisions.txt so that snapcraft can find it.

re-starting xvfb-run too fast makes problems. Trying with -a

GH CD: fix artifact decompaction path

GH CD: try to see content of workdir.

Beremiz revision bump

GH CD: Merge sources and snap dir instead of just giving checkout and artfifact download the same path

Update README.md

GH CD: attempt to preserve content of build/source by swapping checkout and artifact download steps.

Fix generation of revisions.txt in makefile

SNAP: replace lxml versions to be compatible with Beremiz.

Forcing ubuntu20 python-lxml (4.5.0) package instead of PIP vesrion (4.9.1).
4.9.1 leads to derived variable types to appear as "derived" instead of real type name.
Problem happens with plcopen/variables_infos.ysl2 and plcopen/VariableInfoCollector.py.
No clue for now about what really breaks.

Beremiz revision bump