Export -latomic even if BUILD_TESTING is disabled. (backport ros2#516) (ros2#517)

* Export -latomic even if BUILD_TESTING is disabled. (ros2#516)

Signed-off-by: Tomoya Fujita <Tomoya.Fujita@sony.com>
Signed-off-by: Timo Röhling <roehling@debian.org>
(cherry picked from commit 1879f2c)

Author: mergify[bot]

CMakeLists.txt

@@ -150,6 +150,14 @@ endif()
 
 target_link_libraries(${PROJECT_NAME} ${CMAKE_DL_LIBS})
 
+check_library_exists(atomic __atomic_load_8 "" HAVE_LIBATOMICS)
+
+if(HAVE_LIBATOMICS AND NOT WIN32)
+  # Exporting link flag since it won't pass ament_export_libraries() existence check
+  ament_export_link_flags("-latomic")
+  target_link_libraries(${PROJECT_NAME} atomic)
+endif()
+
 # Needed if pthread is used for thread local storage.
 if(IOS AND IOS_SDK_VERSION LESS 10.0)
   ament_export_libraries(pthread)
@@ -177,13 +185,6 @@ if(BUILD_TESTING)
 
   find_package(launch_testing_ament_cmake REQUIRED)
 
-  check_library_exists(atomic __atomic_load_8 "" HAVE_LIBATOMICS)
-
-  if(HAVE_LIBATOMICS AND NOT WIN32)
-    # Exporting link flag since it won't pass ament_export_libraries() existance check
-    ament_export_link_flags("-latomic")
-  endif()
-
   if(ament_cmake_cppcheck_FOUND)
     ament_cppcheck(
       TESTNAME "cppcheck_logging_macros"