Way back in rpm-ostree's original code here, it always assumed
that it owned The Build.
But in a container-native flow we may have a chain of builds
across an organization and want to generate tmpfiles.d entries
multiple times.
When we do this, we can't just blow away the existing `/usr/lib/tmpfiles.d/bootc-generated.conf`.
Teach the tmpfiles code to have "generations" - we pick a new
file name like `bootc-generated-0.conf`, `bootc-generated-1.conf`
etc.
Also, change the generation code to return a struct with more
info about what it did, which will be used in the linting code.
Signed-off-by: Colin Walters <walters@verbum.org>
For the same reason we avoid doing this in other code like
in lints.rs; it's reasonable for someone to mount a volume
on `/var/cache/dnf` for example in a container build, and we
don't want to try to convert it to tmpfiles.d.
Signed-off-by: Colin Walters <walters@verbum.org>
