When I build my package in ROS, I get the following list of warnings:

cc1plus: warning: /usr/lib/x86_64-linux-gnu/libgazebo.so: not a directory
cc1plus: warning: /usr/lib/x86_64-linux-gnu/libgazebo_client.so: not a directory
cc1plus: warning: /usr/lib/x86_64-linux-gnu/libgazebo_gui.so: not a directory
cc1plus: warning: /usr/lib/x86_64-linux-gnu/libgazebo_sensors.so: not a directory
cc1plus: warning: /usr/lib/x86_64-linux-gnu/libgazebo_rendering.so: not a directory
cc1plus: warning: /usr/lib/x86_64-linux-gnu/libgazebo_physics.so: not a directory
cc1plus: warning: /usr/lib/x86_64-linux-gnu/libgazebo_ode.so: not a directory
cc1plus: warning: /usr/lib/x86_64-linux-gnu/libgazebo_transport.so: not a directory
cc1plus: warning: /usr/lib/x86_64-linux-gnu/libgazebo_msgs.so: not a directory
cc1plus: warning: /usr/lib/x86_64-linux-gnu/libgazebo_util.so: not a directory
cc1plus: warning: /usr/lib/x86_64-linux-gnu/libgazebo_common.so: not a directory
cc1plus: warning: /usr/lib/x86_64-linux-gnu/libgazebo_gimpact.so: not a directory
cc1plus: warning: /usr/lib/x86_64-linux-gnu/libgazebo_opcode.so: not a directory
cc1plus: warning: /usr/lib/x86_64-linux-gnu/libgazebo_opende_ou.so: not a directory
cc1plus: warning: /usr/lib/x86_64-linux-gnu/libgazebo_math.so: not a directory
cc1plus: warning: /usr/lib/x86_64-linux-gnu/libgazebo_ccd.so: not a directory
cc1plus: warning: /usr/lib/x86_64-linux-gnu/libboost_thread.so: not a directory
cc1plus: warning: /usr/lib/x86_64-linux-gnu/libboost_signals.so: not a directory
cc1plus: warning: /usr/lib/x86_64-linux-gnu/libboost_system.so: not a directory
cc1plus: warning: /usr/lib/x86_64-linux-gnu/libboost_filesystem.so: not a directory
cc1plus: warning: /usr/lib/x86_64-linux-gnu/libboost_program_options.so: not a directory
cc1plus: warning: /usr/lib/x86_64-linux-gnu/libboost_regex.so: not a directory
cc1plus: warning: /usr/lib/x86_64-linux-gnu/libboost_iostreams.so: not a directory
cc1plus: warning: /usr/lib/x86_64-linux-gnu/libboost_date_time.so: not a directory
cc1plus: warning: /usr/lib/x86_64-linux-gnu/libboost_chrono.so: not a directory
cc1plus: warning: /usr/lib/x86_64-linux-gnu/libboost_atomic.so: not a directory
cc1plus: warning: /usr/lib/x86_64-linux-gnu/libpthread.so: not a directory
cc1plus: warning: /usr/lib/x86_64-linux-gnu/libprotobuf.so: not a directory
cc1plus: warning: /usr/lib/x86_64-linux-gnu/libsdformat.so: not a directory
cc1plus: warning: /usr/lib/x86_64-linux-gnu/libignition-math2.so: not a directory
cc1plus: warning: /usr/lib/x86_64-linux-gnu/libOgreMain.so: not a directory
cc1plus: warning: /usr/lib/x86_64-linux-gnu/libOgreTerrain.so: not a directory
cc1plus: warning: /usr/lib/x86_64-linux-gnu/libOgrePaging.so: not a directory
cc1plus: warning: /usr/lib/x86_64-linux-gnu/libgazebo.so: not a directory
cc1plus: warning: /usr/lib/x86_64-linux-gnu/libgazebo_client.so: not a directory
cc1plus: warning: /usr/lib/x86_64-linux-gnu/libgazebo_gui.so: not a directory
cc1plus: warning: /usr/lib/x86_64-linux-gnu/libgazebo_sensors.so: not a directory
cc1plus: warning: /usr/lib/x86_64-linux-gnu/libgazebo_rendering.so: not a directory
cc1plus: warning: /usr/lib/x86_64-linux-gnu/libgazebo_physics.so: not a directory
cc1plus: warning: /usr/lib/x86_64-linux-gnu/libgazebo_ode.so: not a directory
cc1plus: warning: /usr/lib/x86_64-linux-gnu/libgazebo_transport.so: not a directory
cc1plus: warning: /usr/lib/x86_64-linux-gnu/libgazebo_msgs.so: not a directory
cc1plus: warning: /usr/lib/x86_64-linux-gnu/libgazebo_util.so: not a directory
cc1plus: warning: /usr/lib/x86_64-linux-gnu/libgazebo_common.so: not a directory
cc1plus: warning: /usr/lib/x86_64-linux-gnu/libgazebo_gimpact.so: not a directory
cc1plus: warning: /usr/lib/x86_64-linux-gnu/libgazebo_opcode.so: not a directory
cc1plus: warning: /usr/lib/x86_64-linux-gnu/libgazebo_opende_ou.so: not a directory
cc1plus: warning: /usr/lib/x86_64-linux-gnu/libgazebo_math.so: not a directory
cc1plus: warning: /usr/lib/x86_64-linux-gnu/libgazebo_ccd.so: not a directory
cc1plus: warning: /usr/lib/x86_64-linux-gnu/libboost_thread.so: not a directory
cc1plus: warning: /usr/lib/x86_64-linux-gnu/libboost_signals.so: not a directory
cc1plus: warning: /usr/lib/x86_64-linux-gnu/libboost_system.so: not a directory
cc1plus: warning: /usr/lib/x86_64-linux-gnu/libboost_filesystem.so: not a directory
cc1plus: warning: /usr/lib/x86_64-linux-gnu/libboost_program_options.so: not a directory
cc1plus: warning: /usr/lib/x86_64-linux-gnu/libboost_regex.so: not a directory
cc1plus: warning: /usr/lib/x86_64-linux-gnu/libboost_iostreams.so: not a directory
cc1plus: warning: /usr/lib/x86_64-linux-gnu/libboost_date_time.so: not a directory
cc1plus: warning: /usr/lib/x86_64-linux-gnu/libboost_chrono.so: not a directory
cc1plus: warning: /usr/lib/x86_64-linux-gnu/libboost_atomic.so: not a directory
cc1plus: warning: /usr/lib/x86_64-linux-gnu/libpthread.so: not a directory
cc1plus: warning: /usr/lib/x86_64-linux-gnu/libprotobuf.so: not a directory
cc1plus: warning: /usr/lib/x86_64-linux-gnu/libsdformat.so: not a directory
cc1plus: warning: /usr/lib/x86_64-linux-gnu/libignition-math2.so: not a directory
cc1plus: warning: /usr/lib/x86_64-linux-gnu/libOgreMain.so: not a directory
cc1plus: warning: /usr/lib/x86_64-linux-gnu/libOgreTerrain.so: not a directory
cc1plus: warning: /usr/lib/x86_64-linux-gnu/libOgrePaging.so: not a directory

My CMake file looks like this:

cmake_minimum_required(VERSION 2.8.3)
project(nena_simulation)

## Compile as C++11, supported in ROS Kinetic and newer
add_compile_options(-std=c++11)

find_package(catkin REQUIRED COMPONENTS
  gazebo_ros
  roscpp
  rospy
  controller_manager
  joint_state_controller
  robot_state_publisher
  geometry_msgs
  message_generation
)

find_package(gazebo REQUIRED)

link_directories(${GAZEBO_LIBRARY_DIRS})
include_directories(${Boost_INCLUDE_DIR} ${catkin_INCLUDE_DIRS} ${GAZEBO_INCLUDE_DIRS})

################################################
## Declare ROS messages, services and actions ##
################################################

## Generate messages in the 'msg' folder
add_message_files(
  FILES
  CustomModelState.msg
  CustomPose.msg
)

generate_messages(
  DEPENDENCIES
  geometry_msgs
)

################################################
## Declare ROS dynamic reconfigure parameters ##
################################################

catkin_package(
  INCLUDE_DIRS include
  LIBRARIES gazeboPOSE
  CATKIN_DEPENDS roscpp rospy message_runtime
)

###################################
## catkin specific configuration ##
###################################

###########
## Build ##
###########

include_directories(
  include
  ${catkin_INCLUDE_DIRS}
  ${GAZEBO_LIBRARIES}
)

add_library(gazebo_optitrack src/gazeboPOSE.cpp)
add_dependencies(gazebo_optitrack ${nena_simulation_EXPORTED_TARGETS})
target_link_libraries(gazebo_optitrack ${catkin_LIBRARIES} ${GAZEBO_LIBRARIES})

add_executable(spawn_boxes_node src/spawn_boxes.cpp)
target_link_libraries(spawn_boxes_node ${catkin_LIBRARIES} ${GAZEBO_LIBRARIES})

#############
## Install ##
#############

#############
## Testing ##
#############

I'm not sure where these warnings are coming from and would like to resolve them, if possible. If anybody would know how, that would be much appreciated