New issue by paper42 on void-packages repository

https://github.com/void-linux/void-packages/issues/36642

Description:
#30704 was fixed in xbps (but not yet in a stable release) by @Chocimier in void-linux/xbps#404 in commit:
```
xbps-checkvers: list installed subpackages

Subpackages without main package installed wasn't reported
at all. This can produce duplicates in output, but checkvers'
output isn't good to loop over without passing through
./xbps-src sort-dependencies anyway.
``` 

This causes `show-sys-updates` to show some packages twice and more importantly `update-sys` to build some packages twice.