correctly set -DUSE_QT4=ON flag when needed
Fix compilation error in CI (see https://gepgitlab.laas.fr/humanoid-path-planner/hpp-doc/-/jobs/10230)
Edited by Pierre Fernbach
Fix compilation error in CI (see https://gepgitlab.laas.fr/humanoid-path-planner/hpp-doc/-/jobs/10230)