Updates us to using the newer SDK https://github.com/hexops/sdk-macos-12.0
Also enables cross-compilation of the `mach/gpu` backend for macOS.
Signed-off-by: Stephen Gutekanst <stephen@hexops.com>
This refactors the logic for system SDK inclusion out of the GLFW-specific `build.zig`,
and should make it very easy for anyone to copy this file and start getting cross-platform
builds of their own OpenGL/Vulkan Zig projects.
There may be some libraries we need to add for Vulkan to these SDKs, I haven't yet tested
that - but the overall idea here seems sound.
Fixeshexops/mach#39
Signed-off-by: Stephen Gutekanst <stephen@hexops.com>
