* doc/contributing.texi (Running the Test Suite): Mention that make clean-go may need to be run before running make check-system when previous builds were run with different work trees. Change-Id: I4b68d3a05f1425505816db969284487d725840d6 Signed-off-by: Maxim Cournoyer <maxim.cournoyer@gmail.com> Fixes: https://issues.guix.gnu.org/47573.