As it was not updated, I guess it is not used frequently, so I moved it after the build with pure CMake commands. A possible alternative is that we just get rid of the "Build with ROS msgs compiled in separate colcon workspace" section so users are not confused by two ways of installing the library.
Based on the feedback in https://github.com/robotology/yarp-devices-ros2/issues/63, I guess the section "Build with ROS msgs compiled in separate colcon workspace" was not updated.
As it was not updated, I guess it is not used frequently, so I moved it after the build with pure CMake commands. A possible alternative is that we just get rid of the "Build with ROS msgs compiled in separate colcon workspace" section so users are not confused by two ways of installing the library.