[cmake] work around a Debian/Ubuntu bug in Python install paths
[cmake] work around a Debian/Ubuntu bug in Python install paths

bremond/siconos,siconos/siconos,radarsat1/siconos,fperignon/siconos,siconos/siconos,radarsat1/siconos,radarsat1/siconos,bremond/siconos,siconos/siconos,fperignon/siconos,siconos/siconos,bremond/siconos,fperignon/siconos,bremond/siconos,fperignon/siconos,bremond/siconos,radarsat1/siconos,radarsat1/siconos,fperignon/siconos