When using --basedir, mysql/plugin dir needs to be writable

# sudo -u maxscale bin/maxscale --basedir=/MARIADB

alert  : Opening file '/MARIADB/var//mysql/plugin' for writing failed.: Permission denied.

alert  : MaxScale doesn't have write permission to '/MARIADB/var//mysql/plugin'.

Looking at strace output, access() checks on the plugin dir path only occur when the --basedir option is actually used.

That's why it's not a problem that the default /var/lib64/mysql/plugin is not writable for the maxscale user when using default paths, esp. when using standard package installs.

It only becomes a problem when trying to use the binary tarball, and having all paths local for a non-root install ...