Missing export os depency causes downstream packages to fail

[destogl]

Without this, I get the following error when building a package:

CMake Error at CMakeLists.txt:33 (add_library):
  Target "cool_position_controllers" links to target "tcb_span::tcb_span"
  but the target was not found.  Perhaps a find_package() call is missing for
  an IMPORTED target, or an ALIAS target is missing?


CMake Error at /opt/ros/rolling/share/ament_cmake_gmock/cmake/ament_add_gmock.cmake:69 (add_executable):
  Target "test_position_controller_base" links to target "tcb_span::tcb_span"
  but the target was not found.  Perhaps a find_package() call is missing for
  an IMPORTED target, or an ALIAS target is missing?
Call Stack (most recent call first):
  /opt/ros/rolling/share/ament_cmake_gmock/cmake/ament_add_gmock.cmake:52 (_ament_add_gmock)
  CMakeLists.txt:93 (ament_add_gmock)

Important to mention that I am behind a controller that depends on parameter_traits and my controller is not (directly). Without this propagation of dependencies is bad.