Otherwise modifications to license-files would not invalidate the
module cache.

Fixes: eb52704 ("builder-module: Support recording the LICENSE
information of modules")

(cherry picked from commit ebcc3ae)

Fixes: eb52704 ("builder-module: Support recording the LICENSE
information of modules")

(cherry picked from commit 0ae5378)

(cherry picked from commit f750899)

Fixes: #476
(cherry picked from commit c610181)