Not even that; I've developed for Windows using Wine plus a mingw cross-compiler packaged by the Linux distribution I was using. Another alternative would be ReactOS in a VM.
Some stuff can be built for Macs from Linux, stuff like the Godot game engine supports this.
It is however a guess if they're going to allow that build or not.
I think this is the key insight. I tried to do a similar thing with Windows. The free VM expired every 30 days or so and bootstrapping a build environment each time (even just downloading it) sucked. The build environment is an outlier compared to macOS/Linux/Unix. I eventually ended up paying for Windows. I still couldn't test things like OpenGL inside a VM.
For what it's worth there are many "click and run" virtual machine creators for OS X. It's not acceptable for corporate use because of the license violations, but to be honest I see very little issue for open source developers using such a solution if they don't have a Mac.
In practice if the MacOS support takes more than a quick headers / types update, it will likely need more care in the future as well. That means you need not just a driveby fix, but a continued commitment from someone to ensure compatibility. This is not out of hostility towards the users, but I'll keep calling things that don't work on MacOS cross-platform. (Yes, it sucks; You can vote with your money to stop that situation)