mysql_install_db doesn't detect the base dir anymore

I installed MariaDB from tarball. Usually, I follow the steps that are listed here:

https://mariadb.com/kb/en/mariadb/installing-mariadb-binary-tarballs/

With MariaDB 10.0.20, mysql_install_db returns an error, unless we specify the --basedir.

Since the documentation has not been updated, I think that this is a bug.