New issue by leahneukirchen on void-packages repository

https://github.com/void-linux/void-packages/issues/19589

Description:
If an account has a fixed uid and a pgroup set, the uid is still used as gid (but not created, so this fails).

This is due to

```
                        [ "${_uid}" != "${_uname}" ] && use_id="-u ${_uid} -g ${_uid}"
```

and later

```
                                useradd -c "$descr" -d "$homedir" -s "$shell" ${user_groups} \
                                        ${pgroup:+-N} ${use_id:=-g ${pgroup:-${_uname}}} -r ${_uname} && \
                                        passwd -l ${_uname} >/dev/null 2>&1
```

This needs more logic to handle the case when use_id and pgroup are set.