title: CMake: How to specify VS2015.3 toolset with VS2017 installed
body: <p>I have VS2017 installed, with both VS2017 (v141) and VS2015.3 (v140) toolset installed. I need to generate a solution with CMake and I want CMake to be "fooled" as if VS2015 is installed, so I can build the project with v140 toolset.<br>
  I know this question is possibly a duplicate of: 
  <a href="https://stackoverflow.com/questions/35549164/how-cmake-specify-platform-toolset-for-a-visual-studio-2015-project">How cmake specify &quot;Platform Toolset&quot; for a Visual Studio 2015 project?</a><br>
  But the solution it provides doesn't help me.<br>
  The error messages are:  </p>
  
  <pre><code>Selecting Windows SDK version 10.0.14393.0 to target Windows 10.0.15063.
  The C compiler identification is unknown
  The CXX compiler identification is unknown
  CMake Error at CMakeLists.txt:18 (project):
    No CMAKE_C_COMPILER could be found.
  </code></pre>
  
  <p>I tried installing both VS2017 and VS2015.3 (IDE), but VS2015.3 refused to create even a simple console program.<br>
  Is there another way to generate a solution with v140 toolset?<br>
  (P.S. Don't tell me that I should generate with v141 toolset first and modify the toolset option in Visual Studio. That makes a big difference. )</p>