ignore more build*/ directories
ignore more build*/ directories

--HG--
extra : rebase_source : a9fb20c4a11cde12cb302307986cc00867b024ff

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