Expose Stan Functions: Compile Once and Subsequently Load?

[klattery]

One question is about compiling. Right now it looks like the expose command recompiles the Stan code (which takes time). Is there anyway after compiling once to keep the compiled code in the same directory with Stan code and then subsequently just load the compiled code? This would be directly analogous to what we can do with full Stan code. We compile it once and the next time it can just be loaded (and cmdstanr tells us the model executable is up to date).