Fix the installation of ROOT.
Fix the installation of ROOT.

DESTINATION should be followed by a folder, otherwise we install the
headers one level down.

olifre/root,karies/root,karies/root,olifre/root,karies/root,karies/root,root-mirror/root,root-mirror/root,root-mirror/root,root-mirror/root,olifre/root,karies/root,karies/root,karies/root,olifre/root,olifre/root,olifre/root,karies/root,root-mirror/root,root-mirror/root,olifre/root,olifre/root,root-mirror/root,karies/root,karies/root,karies/root,olifre/root,root-mirror/root,olifre/root,olifre/root,root-mirror/root,root-mirror/root,root-mirror/root