It returns the remote URL from where the sysroot can be downloaded
so that application integrating the tool can use their own
download manager.

Signed-off-by: Louis-Francis Ratté-Boulianne <lfrb@collabora.com>
Reviewed-by: Guillaume Desmottes <guillaume.desmottes@collabora.co.uk>
Differential Revision: https://phabricator.apertis.org/D5207