⚠️ There is a notable spiked pit trap here around
`posix_fallocate()` and `errno`. This has bit other projects,
see e.g.
7bb87460e6
Otherwise the port was straightforward.
subscription-manager has a daemon that runs in a confined domain,
and it doesn't have permission to write usr_t, which is the default
label of /ostree/deploy/$osname/deploy.
A better long term fix is probably to move the origin file into the
deployment root as /etc/ostree/origin.conf or so.
In the meantime, let's ensure the .origin files are labeled as
configuration.
It's better if this is independent from the OstreeSysroot; for
example, a policy is active in a given deployment root at once, not
for a sysroot globally.
We can also collect SELinux-related API in one place.
Unfortunately at the moment there can be only one instance of this
class per process.