There's a merged pull request on the void-packages repository

ladspa-sdk: not all subpackages are noarch
https://github.com/void-linux/void-packages/pull/23533

Description:
The main package ladspa-sdk contains only a header file, but ladspa-sdk-example-plugins and ladspa-sdk-progs subpackages contain arch dependent binaries. Trying to load a plugin fails e.g. on i686.

I think the case where the main package is `noarch`, but some subpackages aren’t isn’t covered (yet) by xbps-src without having to add every available arch to the subpackage (which wouldn’t make sense, anyway). Or is it and I just don’t see it? :)