New review comment by astralchan on void-packages repository

https://github.com/void-linux/void-packages/pull/41675#discussion_r1248570041

Comment:
Since this is targeting the libc, specifically, wouldn't `XBPS_TARGET_LIBC` be more accurate? Something like:

```sh
if [ "$XBPS_TARGET_LIBC" = "musl" ]; then
    makedepends +=" libexecinfo-devel"
fi
```