GTK/X11 is a supported configuration in MacPorts, and not uncommon on legacy systems. If you'd like to drop support, that is completely fine, and we can indicate as much in the MacPorts package. But it would help to throw an error during configuration rather than at build-time. On the other hand if it's a one-line fix then that may be just as easy.
Cannot build 2022c on Mac with X11 GTK
I'm gratified to see them! If you see that gretl gets too far out of date in MacPorts, filing a ticket requesting an update on Trac, or opening a pull request on GitHub, will usually get someone's attention. PS - looks like there is a typo on the Mac Legacy page. "uo-to-date" -> "up-to-date"
MacPorts supports essentially all architectures (PowerPC, i386, x86_64, arm64). Binary packages will be available for most users; to request a "fat" build, use sudo port install gretl +universal This will be x86/arm64, i386/x86, or i386/ppc depending on context. If a binary package is not available, then gretl will be compiled locally.
Link to new MacPorts package
Thanks - building fine now!
CFLAGS passed to C++ compiler
Works for me. You're probably safe switching to CoreServices as early as Darwin 10. (If all goes well here, MacPorts will eventually provide coverage for Darwin 11+. I am currently testing on a Darwin 8 / PowerPC machine.)