cbindgen: Fix adding header dependency on cargo-build

If headers are generated with cbindgen, they should
probably always be available if the rust crate is also
available, so it makes sense to add a dependency.
The changed line was supposed to already do exactly that,
however interface targets are not actually built,
so we need to directly depend on the cargo-build_
custom command that generates the Rust library.
We already do this in other places, it was just
overlooked here.

cmake/Corrosion.cmake

@@ -2119,6 +2119,9 @@ function(corrosion_experimental_cbindgen)
     )
     add_dependencies("_corrosion_cbindgen_${cbindgen_bindings_target}_bindings" "_corrosion_cbindgen_${cbindgen_bindings_target}_bindings_${header_identifier}")
     add_dependencies(${cbindgen_bindings_target} "_corrosion_cbindgen_${cbindgen_bindings_target}_bindings")
+    if(TARGET "${CCN_TARGET}")
+        add_dependencies(cargo-build_${CCN_TARGET} "_corrosion_cbindgen_${cbindgen_bindings_target}_bindings")
+    endif()
 endfunction()
 
 # Parse the version of a Rust package from it's package manifest (Cargo.toml)