[test] Replace symlinks in legacy_cubes by real copies This solves a "python setup.py build" issue on my machine. Copying these files should not be a big deal because they have been dropped in the "default" branch and we would not touch them in 3.26 branch.

missing-dep-for-interpreter make => make | build-essential | dpkg-dev (usr/*/cubicweb/skeleton/debian/rules)
embedded-javascript-library usr/share/cubicweb/cubes/shared/data/jquery.js