Build failing with GCC 8

[urfeex]

On gcc 8 building (more precisely linking) seems to fail. See https://build.ros2.org/job/Hbin_rhel_el864__ur_client_library__rhel_8_x86_64__binary/402/console for example.

IT seems, we explicitly need to link to stdc++fs. We have been discussing this in the ROS 2 Driver repo before: UniversalRobots/Universal_Robots_ROS2_Driver#546

We should fix that here and also add a rhel-based workflow, probably to https://github.com/UniversalRobots/Universal_Robots_Client_Library/blob/master/.github/workflows/industrial-ci.yml based on the docker images published by ros2-controls

Edit: I just manually confirmed that with this change it builds:

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 1449082..65e6376 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -84,6 +84,7 @@ else()
     target_compile_options(urcl PUBLIC -fsanitize=address)
     target_link_options(urcl PUBLIC -fsanitize=address)
   endif()
+  target_link_libraries(urcl PUBLIC stdc++fs)
 endif()