const Id: type = switch (target.os.tag) {
    .linux,
    .dragonfly,
    .netbsd,
    .freebsd,
    .openbsd,
    .haiku,
    .wasi,
    => u32,
    .macos, .ios, .watchos, .tvos => u64,
    .windows => os.windows.DWORD,
    else => usize,
};

Represents an ID per thread guaranteed to be unique only within a process.