mariadb-install-db shows warning on missing directory $pamtooldir/auth_pam_tool_dir

The problem shows up if you compile MariaDB without PAM.
The fix is trivial. Before doing chown, the script should check if directory exists.
Inside the file ./scripts/mysql_install_db.sh
change line 496 from

  if test -z "$srcdir" -a "$in_rpm" -eq 0

to

  if test -z "$srcdir" -a "$in_rpm" -eq 0 -a -d "$pamtooldir/auth_pam_tool_dir"