I just posted on libc-coord about an idea that sounded good, and it
turns out glibc and nearly everyone else have had it for a long time:

https://www.openwall.com/lists/libc-coord/2022/09/19/2

I'd like to bring the same to musl, even though it's not standardized
yet, since it's a clear candidate for standardization and solves a
major problem with the libc DNS API, namely inability to distinguish
NxDomain from NODATA.

Aside from that, it should help justify musl's distinguishing of these
two (very different) results in how search domain fallbacks work and
how results for one of the A or AAAA erroring out get handled. Our
misleadingly reporting "name exists but has no address" as "name
doesn't exist" has made it hard for folks to understand why we don't
keep going on the search when "name does not exist".

Draft patch attached, untested.