What is this undefined reference with -betterC about?

[Dennis]

On Wednesday, 16 June 2021 at 16:27:13 UTC, Dennis wrote:
> It has to be a linker error, dmd cannot know at the time of 
> compiling project A how project B is going to be compiled and 
> vice versa.

Well I suppose you could use a specific dub configuration, maybe 
giving 'hostname' a targetType "sourceLibrary" or something, but 
I would just make the abi consistent.