Remove legacy ament_export_include_directories/libraries calls

[akshar27]

Description

Fixes #3285

rclcpp, rclcpp_action, rclcpp_components and rclcpp_lifecycle all already call ament_export_targets() to export modern CMake targets. Per the issue, that makes the old-style ament_export_include_directories() and ament_export_libraries() calls in each package redundant, so this deletes both (and the now-stale "Export old-style CMake variables" comment above them) from all four CMakeLists.txt files.

Something I found while checking this (left untouched, flagging for review)

rclcpp_action/CMakeLists.txt and rclcpp_lifecycle/CMakeLists.txt each still read ${rclcpp_INCLUDE_DIRS} inside a BUILD_TESTING-only block, to give ament_cmake_cppcheck a hint about include directories coming from outside the package:

set(ament_cmake_cppcheck_ADDITIONAL_INCLUDE_DIRS ${rclcpp_INCLUDE_DIRS})

That variable used to be populated by rclcpp's own ament_export_include_directories() call, which this PR removes. I left both usages alone since (a) this is a cppcheck lint hint, not a functional build/link dependency, and (b) it's out of this issue's stated scope (delete the two calls from these four files). If ${rclcpp_INCLUDE_DIRS} does go empty after this change, the practical effect should just be cppcheck losing some macro-origin hints during the ament_lint_auto cppcheck pass in CI, not a build break — but flagging it explicitly in case a maintainer wants it addressed as a follow-up (possibly by pointing at rclcpp_SOURCE_DIR/rclcpp_INCLUDE_DIRECTORIES from the modern target instead, or similar).

Testing

No local ROS 2/colcon build environment was available, so I verified this differently:

• Confirmed the exact deletions match the issue's instructions precisely (grepped for every ament_export_include_directories/ament_export_libraries call across all four files first, deleted exactly those + the associated stale comment, nothing else).
• Grepped the whole repo's CMakeLists.txt files for any reference to the old-style variables these calls populate (${rclcpp_INCLUDE_DIRS}, ${rclcpp_LIBRARIES}, and the equivalents for the other three packages) to catch any in-repo consumer that might break — found the two cppcheck-hint usages noted above, nothing else.
• Ran cmakelint on all four modified files and compared the warning count against the unmodified upstream files: identical (12/0/20/16 respectively) — this change introduces no new lint warnings, all remaining warnings are pre-existing unrelated line-length flags.

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This PR was written with the help of Claude Code (Claude Sonnet 5), under my direction and review.

🤖 Generated with Claude Code

https://claude.ai/code/session_01Snzt7njUYkxw4oxYJsENbQ

[jmachowinski]

Please verify if the stack builds.
https://docs.ros.org/en/rolling/Get-Started/Installation/Alternatives/Ubuntu-Development-Setup.html