Darwin: ship libSystem.tbd for macOS 13 (Ventura)

[jedisct1]

Add libSystem.13.tbd for macOS Ventura.

[kubkon]

Thanks for this @jedisct1! When upgrading libSystem tbd for a new macOS version, we should update both the TBDs and the libc headers. However, given that macOS 13 is still in beta and won't be released until later this year, I would like to avoid merging any lbc/libsystem bring-up until the actual release date. This is for one simple reason - there is still a high chance they will add/delete/modify some headers / symbol stabs plus I personally don't have Ventura locally therefore cannot verify anything should it go wrong. Once they release the new OS however, I will make merging all required libc/libsystem changes my priority.

[kubkon]

@jedisct1 I will ask you to push any required changes for an update into a different branch however, https://github.com/ziglang/zig/tree/macos-13 with the intention of merging it into master when macOS 13 is actually released. There, we can push all the required changes to Zig to make it compatible with macOS 13. Does that sound OK?

[jedisct1]

Sounds good! 😀