Additional changes for older versions before 9caf157 (5th January 2018)

On that same tab, go to Manage Kits…. Select the default kit and click the Change… button for the CMake Configuration setting. In the edit popup window, add CMAKE_TOOLCHAIN_FILE:STRING=build/mingw32.mingw.cmake or CMAKE_TOOLCHAIN_FILE:FILEPATH=build/mingw32.mingw.cmake as a new line and OK out of both popup windows.

Note: as of 9caf157 (for the master branch) this CMAKE_TOOLCHAIN_FILE:FILEPATH=build/mingw32.mingw.cmake is no longer valid and needs to get removed from the config.