Bug 775: propagate generator when workingaround cmake bug 9220
Bug 775: propagate generator when workingaround cmake bug 9220

rotorliu/eigen,mjbshaw/Eigen,mjbshaw/Eigen,madlib/eigen_backup,madlib/eigen_backup,madlib/eigen_backup,rotorliu/eigen,mjbshaw/Eigen,mjbshaw/Eigen,madlib/eigen_backup,rotorliu/eigen,rotorliu/eigen