This is useful for bind mounting a freshly downloaded and unpacked tar
disk images to /sysroot to mount into.
Specifically, with a kernel command line like this one:
rd.systemd.pull=verify=no,machine,tar:root:http://_gateway:8081/image.tar root=bind:/run/machines/root ip=any
The first parameter downloads the root image, the second one then binds
it to /sysroot so that we can boot into it.
With these settings we intend to turn off timeouts for possibly
interactive/slow commands. The officially documented way to turn off the
time-outs is to setting them to infinity. So far we set them to zero
here though.
This lead to some confusiong, for example #18224. Let's fix this by
uniformly spelling out TimeoutSec=infinity.
This doesn't change behaviour. It just makes our generated files match
what we document, without relying on historic compat support.
Fixes: #18224
Dangling symlinks get pruned when packaging up the installation
directory. Just store empty files instead, and compare the names
rather than the content for .requires/.wants - the filename is
what is important anyway, the content is ignored.
Fixes#22059
