What is this undefined reference with -betterC about?

[jfondren]

On Wednesday, 16 June 2021 at 14:21:40 UTC, jfondren wrote:
>
> Why isn't this linking?

OK, with verbose commands I see that libhostname.a is built 
without -betterC

So that's why this fails to link.

What do I change to
1. a script like this that uses hostname
2. the hostname module

so that both can be built with -betterC when and only when
the script is using -betterC?