This is SO annoying. I can cross compile to Windows from GNU/Linux quite easily. In fact with Wine I can even get MSVC running. But Apple, even though they employ many of the Clang/LLVM developers, believes that you must use their OS to target any Apple product.
Your only reprieve outside of buying their extremely expensive hardware is using CI services like Travis or Github actions.
This has been an issue for decades. Twenty years ago I was doing grid/HPC computing at Sun and there were a lot of bioinformatics firms that used macs and wanted compute clusters of them. It was a huge problem even then.
[0] https://twitter.com/brianstucki/status/800778773998145536
Do you want to be the genius that saved a few dollars on hardware with a Hackintosh only to get the company sued?
It also takes a lot of time to setup so hackintoshing will never gain mainstream numbers.
Looking at System76's equivalent mini, it's $555 for the low end, which has the same RAM and a faster, newer processor. Going to 32 GB takes it all the way to $700, or half what Apple's charging. So yes, "extremely expensive" is what it seems like to me.
Especially given that it should be entirely unnecessary. Just let me do a cross-platform build!
It is a bit of a pain and took me about 45 minutes, but I was going slow.
Of course, if you want to test your software on Macs, you'll have to buy their hardware sooner or later, but even then you have to set up the build on the system instead of keeping it as pure test system.
If you do it for your day job, it's probably justified, but if you are just a hobbyist, then even hundreds of dollars are expensive. Especially if you live in a poorer area or are still a student.