Make `git clean -nxd` silent after `make distclean`
Also check that invariant in CI: After a make distclean
git clean -nxd
should find no files.
The hope is that this catches cases were a make clean
would forget to
list a .gitignore
d file that should either be registered as a
(DIST_)CLEAN_FILES
or should be unignored and committed into the
repository.
Edited by Sebastian Graf