[tlbuild] Solaris 11.4 build error

[Rainer J.H. Brandt]

Thanks, Andreas!

> I've hacked the TWILL changefile for TL'2023 and renamed 'ref_link' to 
> 'ref_lnk'. Thanks for spotting this. (Alternatively, we could add the 
> POSIX-option for Solaris 11.4 and this single WEB code, but I can't test 
> this approach.)

With the updated weav-twill.ch, the build runs smoothly and the resulting
installation works nicely.

If I can help with testing anything else, I will do that.

Cheers, Rainer