Fix use of AMENT_PREFIX_PATH

[traversaro]

The AMENT_PREFIX_PATH environment variable can be used to specify non-standard directory and prefixes that are looked into for the ament_index (https://github.com/ament/ament_index), that is the resource retrieval system used by ROS2. However, in this repo and in several other repos (icub-models, idyntree) we assumed that for a given <install_prefix>, <install_prefix>/share should be added to AMENT_PREFIX_PATH. However, this is wrong, and even if I can't find a clear documentation page for AMENT_PREFIX_PATH, by using ament_index and inspecting the source code of ament-related code (for example https://github.com/ament/ament_cmake/blob/84e1cea2df62102509de530a5b1bb6d8cde2b5a2/ament_cmake_core/cmake/index/ament_index_get_prefix_path.cmake#L37 ) it is clear that <install_prefix> should be appended to AMENT_PREFIX_PATH, not <install_prefix>\share.

[traversaro]

I wonder if the same problem affects pinocchio: https://github.com/stack-of-tasks/pinocchio/blob/a1df23c2f183d84febdc2099e5fbfdbd1fc8018b/src/utils/file-explorer.cpp#L48 , that is the original space from which we took the inspiration.

[traversaro]

To double check, I installed ROS Noetic and ROS Foxy in a machine and I checked the value of this env vars, see:

codespace ➜ ~ $ rosversion -d
noetic
codespace ➜ ~ $ echo $ROS_PACKAGE_PATH 
/opt/ros/noetic/share

and

codespace ➜ /workspaces/robotology-superbuild (master ✗) $ echo $AMENT_PREFIX_PATH 
/opt/ros/foxy

Indeed, AMENT_PREFIX_PATH contains <prefix>, while ROS_PACKAGE_PATH contains <prefix>/share .

[traversaro]

This will be fixed by the following PRs:

• Fix used values of AMENT_PREFIX_PATH #868
• Fix AMENT_PREFIX_PATH documentation icub-models#101
• SolidShapes: Fix handling of AMENT_PREFIX_PATH idyntree#915