title: CMake: how to properly setup new toolchain to avoid "System is unknown to CMake" message?
body: <p>I have setup a new CMake toolchain file to cross-compile for the STxP70 processor. I placed the file in my working directory and simply call cmake using:</p>
  
  <pre><code>$ cmake -DCMAKE_TOOLCHAIN_FILE=STxP70_toolchain.cmake ...
  </code></pre>
  
  <p>It works properly, but I always get a message that says:</p>
  
  <pre><code>System is unknown to cmake, create:
  Platform/STxP70 to use this system, please send your config file to cmake@www.cmake.org so it can be added to cmake
  </code></pre>
  
  <p>Is there a way to place the toolchain file somewhere locally so that CMake will recognize it and not complain that the system is unknown? I can't seem to find it anywhere.</p>
  
  <p>Thanks in advance. </p>