Bring ament_add_gtest/target_link_libraries back together (ros2#452)

Signed-off-by: Christophe Bedard <christophe.bedard@apex.ai>

Author: christophebedard

CMakeLists.txt

@@ -568,6 +568,9 @@ if(BUILD_TESTING)
   ament_add_gtest(test_macros
     test/test_macros.cpp
   )
+  if(TARGET test_macros)
+    target_link_libraries(test_macros ${PROJECT_NAME})
+  endif()
 
   add_performance_test(benchmark_logging test/benchmark/benchmark_logging.cpp)
   if(TARGET benchmark_logging)
@@ -578,10 +581,6 @@ if(BUILD_TESTING)
   if(TARGET benchmark_err_handle)
     target_link_libraries(benchmark_err_handle ${PROJECT_NAME})
   endif()
-
-  if(TARGET test_macros)
-    target_link_libraries(test_macros ${PROJECT_NAME})
-  endif()
 endif()
 
 # Export old-style CMake variables