New review comment by ericonr on void-packages repository

https://github.com/void-linux/void-packages/pull/23515#discussion_r453150642

Comment:
Most of the other helpers seem to add stuff unconditionally. Why not here?

It could work like `add numpy helper -> numpy is added as a depend in the appropriate places, no need to worry about it`, or do you think people should still list `python3-numpy` somewhere in their dependencies? If so, what's the correct place?

I would have something like

```
makedepends+=" python3-numpy"

if [ "$CROSS_BUILD" ]; then
  hostmakedepends+=" python3-numpy"
[...]
```