Packages that are looking for "ROS_VERSION" fail

[rkent]

Some packages use conditional values in package.cml, like:

<export>
    <!-- We need catkin installed during builds so debian/rules finds /opt/*/setup.bash -->
    <build_type condition="$ROS_VERSION == 1">catkin</build_type>
    <build_type condition="$ROS_VERSION == 2">cmake</build_type>
</export>

rosdoc2 is ROS 2 only, but these packages are not getting the correct build_type, so Doxygen is not running.

One example is mp2p_icp (though there are other reasons there why Doxygen is not running).