cbindgen swept transport/udp.rs's `recvmsg_x` foreign import and its `MsghdrX`
#[repr(C)] struct into the generated C header — they're internal Apple-only FFI,
not part of the public C ABI, and reference socklen_t/ssize_t/iovec which the C
ABI harness doesn't include, so c_abi_harness_round_trips failed to compile.
Add them to cbindgen.toml export.exclude and regenerate the header.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
enricobuehler
cc0f864e09