Missing target to generate librust_part.a

[StephanBischoff-Digle]

Hey, I was trying to use this project as a template to generate a static lib from a crate and a cpp executable and found that the executable target could not be generated due to the missing librust_part.a. If the target for the rust lib was build first everything went fine in a second stage when the executable was built.

I added ${RUST_PART_LIB} as an OUTPUT to the add_custom_command directive in the rust_part/CMakeLists.txt which lets cmake know that librust_part.a is generated by that command. Now it appears to build everything alright in one go.

Is there any reason why this could be not OK?