ros-noetic-joy doesn't install joy-node when built on non-linux systems

So this is an interesting one..

the CmakeList.txt for ros-noetic-joy includes a check to see if it's running on a system that includes the linux kernel joystick headers, if not, it skips installing joy_node. It does raise a warning for this but it doesn't make it to the pixi/conda user.

Now, that isn't very robostack behaviour given that joy is listed as available for platforms other than linux. It leads to errors when using pre-made sim environments, like the husky gazebo package, which actively interacts with joy_node.

This seems to not be an issue in the ros2 joy package as they switched to the platform agnostic sdl2 library for joystick interfacing.

Opening this issue to track making a patch for ros-noetic-joy that falls back to sdl2 if it doesn't detect linux/joystick.h and still builds joy_node (also to see if anyone else has attempted this before and can tell me if it's a fools errand).

There's also https://github.com/mikepurvis/joystick_sdl which might give us some clues, but it's about 10 years old and was only ever released on ros-indigo.

Start with joy/CMakeLists.txt and its linux/joystick.h check, then compare the ROS 2 joy package and the referenced joystick_sdl project. The work is done when ros-noetic-joy builds on non-Linux systems with joy_node available and the husky_control teleop.launch use case no longer fails.