title: CMake: how to change compiler for individual target
body: <p>I have embedded project using cross compiler. I would like to introduce Google test, compiled with native GCC compiler. Additionally build some unit test targets with CTC compiler.  </p>
  
  <p><em>Briefly:</em><br>
  I have 3 different targets and compile them with 3 different compilers. How to express it in <strong>CMakeLists.txt</strong>? I Tried <code>SET_TARGET_PROPERTIES</code>;<br>
  but it seems impossible to set <code>CXX variable</code> with this command!</p>