fix installation of global headers in case the src path contains 'src'
fix installation of global headers in case the src path contains 'src'

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