How to export header and library build flags for non-catkin projects?

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For some of our in-house ROS nodes, I want to link against some of our proprietary headers and libraries, none of which are built using catkin or cmake. What I would like to do is create a ROS package that acts as a wrapper, so that all my other ROS packages can just list the wrapper package as a dependency, and all the include and library C++ flags that point to our proprietary software are automatically included. What's the most efficient way to do that?