rive-app/rive-runtime ? reverse-engineered prompt

Build me the Rive C++ runtime project so I can load .riv files, play animations and state machines, and render them in a simple sample app.

I want the repo to build cleanly on my machine, include the core runtime library, the GPU renderer, and the player app that opens a Rive file and draws it on screen. Please make sure the tests run too, especially the image comparison ones, and fix anything obvious if the build or sample app is broken.

If you need to check the current setup details or the right build steps, look up the latest docs online and use the repo’s existing scripts. Keep it working for a normal developer who just wants to clone the project, build it, and see a Rive animation rendered successfully.