Fixes #6727 The major change in this commit is to consolidate all the C imports in a single decl in main.zig. This is required for Zig 0.14. Without it, the problem in #6727 will happen. I was never able to minimize why this happens in order to open a Zig bug. Beyond this, I fixed the build.zig and build.zig.zon to work with Zig 0.14 so that we can test building `pkg/macos` in isolation. There are no downstream impacting changes in the build.zig files.