This adds `setpwent()`, `getpwent_r()`, `endpwent()`, `setgrent()`,
`getgrent_r()`, and `endgrent()` interfaces to nss-systemd library.
Thus, dynamic users can be enumerated by e.g. `getent passwd` command.
Meson keeps permissions around during the build, so details of how umask
was set when cloning the original git tree will leak all the way to the
installed files in the mkosi image.
So reset the permissions of the files in the copy of the tree before
starting the build.
Also set the umask explicitly.
Tested by creating a mkosi image and booting it on a tree that was
cloned with a umask of 027, confirmed that the *.target files were not
created as world-unreadable anymore.
In commit da1921a5c3 ppc64/ppc64el were added as supported architectures for
socketcall() for the POWER family. Extend the support for the 32bits
architectures.
Commit 563dc6f8e2 added support for
/etc/{passwd,group} only but since nsswitch.conf(5) appears to document the NIS
entries also for shadow, let's support this case too.
Similar to 16bed3afa1, this model also doesn't have the
LED.
```
cat /sys/class/dmi/id/modalias
dmi:bvnLENOVO:bvrN1KET16W(1.03):bd01/20/2016:svnLENOVO:pn20FH001AMX:pvrThinkPadT560:rvnLENOVO:rn20FH001AMX:rvrSDK0J40705WIN:cvnLENOVO:ct10:cvrNone:
```