There is a VS2015 project which is generated by CMake and I want to change its \"Platform Toolset\".
Using CMAKE_GENERATOR_TOOLSET is better than using the -T option.
CMAKE_GENERATOR_TOOLSET
-T
It's not required to remove the CMakeCache.txt file when re-generating CMake.
e.g.
cmake -G "Visual Studio 16" -A Win32 -DCMAKE_GENERATOR_TOOLSET=v140