Fixed colcon build args

[CihatAltiparmak]

Added --symlink-install arg to colcon build command. Otherwise nav2_common may give build error. Additionaly, it would be great to apply direction inside navigation2 repo : https://github.com/ros-navigation/navigation2/blob/44a69ccde93514ed1a962b7f18cb101ec671d93a/Dockerfile#L119

[SteveMacenski]

What error appeared? I generally prefer on a personal basis not to do symlinks, but that's not a good justification for keeping it that way if there's a technical reason to change it for Docker developer's use

[CihatAltiparmak]

For my case, i'm trying to implement a kind of nav2 controller and when i compiled with colcon build --packages-up-to nav2_frenet_ilqr_controller --symlink-install, i receive some below error. (i sourced ros-rolling before) I can solve it, however i decided to send PR when i took a look at navigation2' dockerfile.

root@jarbay51:~/nav2_ws# colcon build --packages-up-to nav2_frenet_ilqr_controller --symlink-install
Starting >>> nav2_common
Starting >>> frenet_trajectory_planner
--- stderr: nav2_common                                                                               
failed to create symbolic link '/root/nav2_ws/build/nav2_common/ament_cmake_python/nav2_common/nav2_common' because existing path cannot be removed: Is a directory
gmake[2]: *** [CMakeFiles/ament_cmake_python_symlink_nav2_common.dir/build.make:70: CMakeFiles/ament_cmake_python_symlink_nav2_common] Error 1
gmake[1]: *** [CMakeFiles/Makefile2:138: CMakeFiles/ament_cmake_python_symlink_nav2_common.dir/all] Error 2
gmake: *** [Makefile:124: all] Error 2
---
Failed   <<< nav2_common [0.54s, exited with code 2]
Aborted  <<< frenet_trajectory_planner [1.33s]                            

Summary: 0 packages finished [1.50s]
  1 package failed: nav2_common
  1 package aborted: frenet_trajectory_planner
  1 package had stderr output: nav2_common
  9 packages not processed
root@jarbay51:~/nav2_ws# 

In addition of this, i think whether OVERLAY_MIXINS should be added or not but anyway.

[SteveMacenski]

Maybe its worth having an ARG for generic build settings that you could use to set symlink install (or other potential mods). I’d merge that so you could build it with the flags you like but by default not symlinking from our package index. If building with symlink, you need to always build with symlink, so it doesn’t seem like good general purpose behavior, unless we also provide a “nav2 build” command which sets the build settings so that an end user doesnt need to call colcon. I’d also be open to that, that’s not so uncommon - though adds some Getting Started onboarding friction for new users that we need to document