[ROS 2] Use octomap target directly

[sloretz]

This fixes a compile error from missing include directories when building both geometry_shapes and octomap in the same workspace.

--- stderr: geometric_shapes                                                                                                                
/home/sloretz/ws/sdfurdf/src/geometric_shapes/src/shapes.cpp:39:10: fatal error: octomap/octomap.h: No such file or directory
   39 | #include <octomap/octomap.h>
      |          ^~~~~~~~~~~~~~~~~~~
compilation terminated.
make[2]: *** [CMakeFiles/geometric_shapes.dir/build.make:154: CMakeFiles/geometric_shapes.dir/src/shapes.cpp.o] Error 1
make[1]: *** [CMakeFiles/Makefile2:127: CMakeFiles/geometric_shapes.dir/all] Error 2
make: *** [Makefile:141: all] Error 2
---
Failed   <<< geometric_shapes	[ Exited with code 2 ]

The problem comes from octomap exporting variables beginning with all uppercase OCTOMAP_ when the CMake package is found using lowercase octomap. This prevents ament_target_dependencies from adding those variables to the given target. This PR solves the issue by using the imported target octomap instead.

[sloretz]

I should note, I'm testing this building ros2 from source from master branches. I haven't tried the same scenario in ROS Dashing, Eloquent, or Foxy.

[codecov]

Codecov Report

Merging #150 into dashing-devel will not change coverage.
The diff coverage is n/a.

@@              Coverage Diff               @@
##           dashing-devel     #150   +/-   ##
==============================================
  Coverage          55.78%   55.78%           
==============================================
  Files                 12       12           
  Lines               1719     1719           
==============================================
  Hits                 959      959           
  Misses               760      760           

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[henningkayser]

Thanks @sloretz. Actually, I think we should use the all capital letters target OCTOMAP with ament_target_dependencies - this one should provide libraries and include directories.

[henningkayser]

I added a related fix to #153 as part of preparing the Foxy release. On what ROS2 distribution have you been testing this (Crystal?). We didn't plan on actively supporting older versions than Foxy anymore as we are also moving to Foxy with MoveIt 2.

[henningkayser]

Closing since fix has been added with #153