soapysdr-sys builds bindings with bindgen, which needs libclang at build time. Add clang and libclang-dev to the system dependencies so the soapysdr backend (a default feature) compiles under CI. Assisted-By: Claude Code (claude-opus-4) Claude-Session: https://claude.ai/code/session_01NFpGtGTWUEYXLwZeZs2RAV Signed-off-by: Stan Grams <sjg@haxx.space>