macOS builds appear broken

Some of the recent bot PRs for updating dependencies have failed on macOS. [Here](https://github.com/oxidecomputer/usdt/actions/runs/11802773584/job/32879187433?pr=328#step:4:452) is a link to the error I see for all of them. That points to the file `/usr/lib/dtrace/tcp.d`, which is a system-provided D file with what looks like definitions of a bunch of TCP-related types, presumably to support tracing TCP connections and traffic. The error is complaining about an "invalid type identifier" for a `struct tcpcb*`. That type is defined just below the line where the failure appears, so I'm not sure what the issue is. I should also note that this is failing on macOS 14.7.1. I am running 14.6.1 locally, and I see no such failure.