Systemd Adds Optional Rust Support

Systemd developers added optional support for Rust programs to the systemd Git repository today, allowing leaf components to be written in Rust instead of C. The new systemd-keyring-setup utility handles keyring provisioning during boot, though core library code remains in C. Rust components are slightly larger than C equivalents and are toggled by the -Drust= Meson option, defaulting to auto.