To update this port:
Bump DISTVERSION
eventually bump WEBRTC_REV (sh net-im/signal-desktop/get_deps.sh)
eventually update *_REV (sh multimedia/ringrtc/webrtc_fetch.sh)
eventually update CARGO_CRATES (fetch -qo - https://raw.githubusercontent.com/signalapp/ringrtc/vXXX/src/rust/Cargo.lock | awk -f /usr/ports/Mk/Scripts/cargo-crates.awk | portedit merge -i Makefile)