title: Supressing warning in building Opencv with Cmake
body: <p>I have a warning in building Opencv using Cmake. It suggests "Use -Wno-dev to suppress it.". But I don't know how to suppress it.</p>
  
  <p>The warnings come out when I do "generate" in ccmake GUI.
  The warnings are</p>
  
  <pre><code> CMake Warning (dev) at apps/haartraining/CMakeLists.txt:34 (add_library):
     Policy CMP0038 is not set: Targets may not link directly to themselves.
     Run "cmake --help-policy CMP0038" for policy details.  Use the cmake_policy
     command to set the policy and suppress this warning.
  
     Target "opencv_haartraining_engine" links to itself.
   This warning is for project developers.  Use -Wno-dev to suppress it.
  
  
   CMake Warning (dev) at apps/haartraining/CMakeLists.txt:34 (add_library):
     Policy CMP0038 is not set: Targets may not link directly to themselves.
     Run "cmake --help-policy CMP0038" for policy details.  Use the cmake_policy
     command to set the policy and suppress this warning.
  
     Target "opencv_haartraining_engine" links to itself.
   This warning is for project developers.  Use -Wno-dev to suppress it.
  
  
  
  Messages during last pass                                                       
                                                               CMake Version 3.2.2
  Press [e] to exit help
  </code></pre>
  
  <p>How to remove this warnings? This is just warning, but can't proceed this step when I press 'e', ccmake GUI stops. So ccmake doesn't generate anything and stops.
  Thanks</p>