We are using cbindgen to auto generate our C bindings. Install the tool via:
cargo install cbindgen
cbindgen $FUCHSIA_DIR/garnet/lib/rust/wlan-mlme-c/ -o $FUCHSIA_DIR/garnet/lib/rust/wlan-mlme-c/bindings.h
After re-generating the bindings also run fx format-code to format the generated bindings.