use file generate to create pointer to default plugin lib

src/rviz/default_plugin/CMakeLists.txt

@@ -80,23 +80,10 @@ install(TARGETS ${rviz_DEFAULT_PLUGIN_LIBRARY_TARGET_NAME}
   LIBRARY DESTINATION ${CATKIN_PACKAGE_LIB_DESTINATION})
 
 # Generate to the devel space so the extras file can include it from the devel space.
-add_custom_command(
-  OUTPUT ${CATKIN_DEVEL_PREFIX}/${CATKIN_PACKAGE_SHARE_DESTINATION}/cmake/default_plugin_location.cmake
-  COMMAND
-    ${CMAKE_COMMAND}
-    -DPATH_TO_FILE="${CATKIN_DEVEL_PREFIX}/${CATKIN_PACKAGE_SHARE_DESTINATION}/cmake/default_plugin_location.cmake"
-    -DDEFAULT_PLUGIN_FILE_NAME=$<TARGET_FILE_NAME:${rviz_DEFAULT_PLUGIN_LIBRARY_TARGET_NAME}>
-    -P ${CMAKE_CURRENT_SOURCE_DIR}/file_generate_helper.cmake
+file(GENERATE
+  OUTPUT "${CATKIN_DEVEL_PREFIX}/${CATKIN_PACKAGE_SHARE_DESTINATION}/cmake/default_plugin_location.cmake"
+  CONTENT "set(rviz_DEFAULT_PLUGIN_FILE_NAME $<TARGET_FILE_NAME:${rviz_DEFAULT_PLUGIN_LIBRARY_TARGET_NAME}>)"
 )
-add_custom_target(create_default_plugin_location_file ALL
-  DEPENDS ${CATKIN_DEVEL_PREFIX}/${CATKIN_PACKAGE_SHARE_DESTINATION}/cmake/default_plugin_location.cmake
-)
-# TODO(wjwwood): remove the solution above (including the file_generate_helper.cmake file) when we can
-# depend on cmake >= 2.8.12 (after dropping Saucy) and use the snippet below.
-# file(GENERATE
-#   OUTPUT "${CATKIN_DEVEL_PREFIX}/${CATKIN_PACKAGE_SHARE_DESTINATION}/cmake/default_plugin_location.cmake"
-#   CONTENT "set(rviz_DEFAULT_PLUGIN_FILE_NAME $<TARGET_FILE_NAME:${rviz_DEFAULT_PLUGIN_LIBRARY_TARGET_NAME}>)"
-# )
 # Install from the devel space to the install space.
 install(FILES "${CATKIN_DEVEL_PREFIX}/${CATKIN_PACKAGE_SHARE_DESTINATION}/cmake/default_plugin_location.cmake"
   DESTINATION ${CATKIN_PACKAGE_SHARE_DESTINATION}/cmake