<p>The error you have made is that the MSVC15 macro is not one that exists.  If you read the CMake documentation you would see that Visual Studio 2015 is represented by the MSVC14 macro:<br>
<a href="https://cmake.org/cmake/help/v3.1/variable/MSVC14.html">https://cmake.org/cmake/help/v3.1/variable/MSVC14.html</a></p>

<p>I cannot accept this patch until it is tested to ensure that it doesn't break anything; so it must be tested on Windows with Visual Studio 2015 to ensure that it still works, and also on at least one earlier version of Visual Studio to ensure that the CMake configuration fails.</p>

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