Currently the WESTON_USER variable is used as user and group name for
chown'ing XDG_RUNTIME_DIR. If WESTON_USER has no group with the same
name this fails.
Therefore add a new WESTON_GROUP variable which is set to WESTON_USER if
not specified to ensure backwards compatibility.
Signed-off-by: Richard Leitner <richard.leitner@skidata.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
