From systemd-repart(8):
If not specified it is attempted to read the machine ID from the host
(or more precisely, the root directory configured via --root=) and use
it as seed instead, falling back to a randomized seed otherwise. Use
--seed=random to force a randomized seed.
The option documentation now suggests the special value "random", for
a random seed rather than relying on the implicit fact that there is
no machine ID available in the build sandbox, causing repart to fallback
on generating a random seed.
Fixes#419331
ed5f0fbfcd