The latest Zig master supports specifying a specific macOS version for libc, via
the target triple (ziglang/zig#10215):
* x86_64-macos.10 (Catalina)
* x86_64-macos.11 (Big Sur)
* x86_64-macos.12 (Monterey)
* aarch64-macos.11 (Big Sur)
* aarch64-macos.12 (Monterey)
Mach's `system_sdk.zig` can now download the relevant XCode framework stubs
for Big Sur (11) and Monterey (12). Although we don't have an SDK for Catalina (10)
currently, we use the Big Sur (11) SDK in that case and it generally works fine.
By default, Zig targets the N-3 version (e.g. `x86_64-macos` defaults to `x86_64-macos.10`).
Targeting the minimum supported version is useful for compatability, it guarantees the produced
binary will run on any later macOS version. Targeting the newer version can be useful if you
wish to use newer APIs not available in previous versions.
Fixeshexops/mach#102
Signed-off-by: Stephen Gutekanst <stephen@hexops.com>