Remove symlink loops in engine-plugins

[scpeters]

🦟 Bug fix

Fixes gz-sim test failures with PR chain in gazebosim/gz-sim#2910, part of gazebo-tooling/release-tools#1309

Summary

When testing the remaining Jetty version bumps (such as gazebosim/gz-sim#2910), I ran a colcon build:

• https://build.osrfoundation.org/job/ci__colcon_any-manual_ubuntu_noble_amd64/34/

and noticed two gz-sim test failures in particular the seem related to symlinked physics plugins:

• INTEGRATION_pose_publisher_system
• INTEGRATION_save_world

In both cases:

[ RUN      ] PosePublisherTest.NestedModelLoadPlugin
(2025-05-17 19:47:41.276) [info] [ServerPrivate.cc:656] Loading SDF world file[/tmp/ws/src/gz-sim/test/worlds/nested_model.sdf].
(2025-05-17 19:47:41.344) [info] [SystemManager.cc:54] Serving entity system service on [/entity/system/add]
unknown file: Failure
C++ exception with description "filesystem error: status: Too many levels of symbolic links [/tmp/ws/install_isolated/gz-physics/lib/gz-physics-9/engine-plugins/libgz-physics-tpe-plugin.so]" thrown in the test body.
[  FAILED  ] PosePublisherTest.NestedModelLoadPlugin (102 ms)

Since there are no more versioned libraries, we should just remove these symlinks.

I will start a colcon build including this branch after confirming it doesn't break this package's CI.

Checklist

• Signed all commits for DCO
• Added tests
• Updated documentation (as needed)
• Updated migration guide (as needed)
• Consider updating Python bindings (if the library has them)
• codecheck passed (See contributing)
• All tests passed (See test coverage)
• While waiting for a review on your PR, please help review another open pull request to support the maintainers

Note to maintainers: Remember to use Squash-Merge and edit the commit message to match the pull request summary while retaining Signed-off-by messages.

[scpeters]

colcon build with this branch (using gazebo-tooling/gazebodistro@a3c44ca):

• https://build.osrfoundation.org/job/ci__colcon_any-manual_ubuntu_noble_amd64/35/
• https://build.osrfoundation.org/job/ci__colcon_any-manual_ubuntu_noble_amd64/36/

[scpeters]

colcon build with this branch (using gazebo-tooling/gazebodistro@a3c44ca):

• https://build.osrfoundation.org/job/ci__colcon_any-manual_ubuntu_noble_amd64/36/

this fixes the tests

223: Test command: /tmp/ws/build_isolated/gz-sim/bin/INTEGRATION_save_world "--gtest_output=xml:/tmp/ws/build_isolated/gz-sim/test_results/INTEGRATION_save_world.xml"
...
223: [ RUN      ] SdfGeneratorFixture.WorldWithNestedModel
223: Loading: /tmp/ws/src/gz-sim/test/worlds/nested_model.sdf
223: (2025-05-18 07:43:05.886) [info] [ServerPrivate.cc:656] Loading SDF world file[/tmp/ws/src/gz-sim/test/worlds/nested_model.sdf].
223: (2025-05-18 07:43:05.949) [info] [SystemManager.cc:54] Serving entity system service on [/entity/system/add]
223: (2025-05-18 07:43:05.952) [debug] [Physics.cc:889] Loaded [gz::physics::tpeplugin::Plugin] from library [/tmp/ws/install_isolated/gz-physics/lib/gz-physics-9/engine-plugins/libgz-physics-tpe-plugin.so]
223: (2025-05-18 07:43:05.952) [debug] [SystemManager.cc:80] Loaded system [gz::sim::systems::Physics] for entity [1]
223: (2025-05-18 07:43:05.952) [debug] [SystemManager.cc:80] Loaded system [gz::sim::systems::SceneBroadcaster] for entity [1]
223: (2025-05-18 07:43:05.954) [debug] [SystemManager.cc:80] Loaded system [gz::sim::systems::PosePublisher] for entity [8]
223: (2025-05-18 07:43:05.954) [info] [LevelManager.cc:641] Loaded level [default]
223: (2025-05-18 07:43:05.954) [debug] [ServerConfig.cc:1025] Loading (3) plugins from file [/tmp/ws/build_isolated/gz-sim/test/fake_home/.gz/sim/10/server.config]
223: (2025-05-18 07:43:05.954) [debug] [SimulationRunner.cc:1645] Additional plugins to load:
223: (2025-05-18 07:43:05.954) [debug] [SimulationRunner.cc:1648] gz::sim::systems::UserCommands gz-sim-user-commands-system
223: (2025-05-18 07:43:05.955) [info] [UserCommands.cc:664] Create service on [/world/nested_model_world/create]
223: (2025-05-18 07:43:05.955) [info] [UserCommands.cc:671] Remove service on [/world/nested_model_world/remove]
223: (2025-05-18 07:43:05.955) [info] [UserCommands.cc:678] Pose service on [/world/nested_model_world/set_pose]
223: (2025-05-18 07:43:05.955) [info] [UserCommands.cc:686] Pose service on [/world/nested_model_world/set_pose_vector]
223: (2025-05-18 07:43:05.955) [info] [UserCommands.cc:693] Light configuration service on [/world/nested_model_world/light_config]
223: (2025-05-18 07:43:05.955) [info] [UserCommands.cc:719] Physics service on [/world/nested_model_world/set_physics]
223: (2025-05-18 07:43:05.955) [info] [UserCommands.cc:727] SphericalCoordinates service on [/world/nested_model_world/set_spherical_coordinates]
223: (2025-05-18 07:43:05.956) [info] [UserCommands.cc:736] Enable collision service on [/world/nested_model_world/enable_collision]
223: (2025-05-18 07:43:05.956) [info] [UserCommands.cc:745] Disable collision service on [/world/nested_model_world/disable_collision]
223: (2025-05-18 07:43:05.956) [info] [UserCommands.cc:754] Material service on [/world/nested_model_world/visual_config]
223: (2025-05-18 07:43:05.956) [info] [UserCommands.cc:762] Material service on [/world/nested_model_world/wheel_slip]
223: (2025-05-18 07:43:05.956) [debug] [SystemManager.cc:80] Loaded system [gz::sim::systems::UserCommands] for entity [1]
223: (2025-05-18 07:43:05.956) [info] [SimulationRunner.cc:260] Serving world controls on [/world/nested_model_world/control], [/world/nested_model_world/control/state] and [/world/nested_model_world/playback/control]
223: (2025-05-18 07:43:05.956) [info] [SimulationRunner.cc:286] Serving GUI information on [/world/nested_model_world/gui/info]
223: (2025-05-18 07:43:05.956) [info] [SimulationRunner.cc:289] World [nested_model_world] initialized with [1ms] physics profile.
223: (2025-05-18 07:43:05.956) [info] [SimulationRunner.cc:296] Serving world SDF generation service on [/world/nested_model_world/generate_world_sdf]
223: (2025-05-18 07:43:05.956) [info] [ServerPrivate.cc:336] Serving world names on [/gazebo/worlds]
223: (2025-05-18 07:43:05.957) [info] [ServerPrivate.cc:349] Resource path add service on [/gazebo/resource_paths/add].
223: (2025-05-18 07:43:05.957) [info] [ServerPrivate.cc:362] Resource path get service on [/gazebo/resource_paths/get].
223: (2025-05-18 07:43:05.957) [info] [ServerPrivate.cc:377] Resource path resolve service on [/gazebo/resource_paths/resolve].
223: (2025-05-18 07:43:05.957) [info] [ServerPrivate.cc:391] Resource paths published on [/gazebo/resource_paths].
223: (2025-05-18 07:43:05.957) [info] [ServerPrivate.cc:404] Server control service on [/server_control].
223: [       OK ] SdfGeneratorFixture.WorldWithNestedModel (268 ms)

[scpeters]

building nightly

• https://build.osrfoundation.org/job/gz-physics9-debbuilder/77/