Feature/mac os steps and support

[Bergasms]

There were a few comments on the zig-vulkan-triangle project asking about getting it working on macOS. This PR addresses that although I'm not sure if it's in an acceptable way or not.

I'm a zig novice, the changes to the build.zig have involved a lot of trial and error because I don't fully understand a lot of them and have essentially reverse engineered from example build files that I could find online.

I haven't tested that this doesn't break on systems OTHER than macOS, it shouldn't but again, I'm a beginner.

I haven't ever done much work with git pull requests on GitHub with someone else's projects, I have no idea if this is how people do it or not. Hopefully you find this useful, if there are changes I should make before it becomes acceptable let me know, or if you're not interested that is fine too.