CMake Tools 1.4.0 doesn't define CMAKE_BUILD_TYPE in a project's build directory's CMakeCache.txt

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### Brief Issue Summary

I am using Visual Studio Code and CMake Tools to build a simple C++ project using OpenCV. The project relies on OpenCV's opencv_world430d.dll and OpenCV_world.dll files. To copy them to the build and install directory, I use an if statement to check whether the CMAKE_BUILD_TYPE matches either Debug or Release; then I define a variable equal to the path to the corresponding debug or release dll. Lastly, I use a custom command to copy the files to the build directory and install them to a desired install location. The problem is, CMAKE_BUILD_TYPE is not defined - even though I've configured the project and selected a Debug configuration.

### Expected:

If build type is Debug, the syntax if(${CMAKE_BUILD_TYPE) MATCHES Debug) should return true; else, if build type is Release, the syntax if(${CMAKE_BUILD_TYPE) MATCHES Release) should return true.

It is expected that CMAKE_BUILD_TYPE is defined as either Debug or Release.

### Apparent Behavior

CMAKE_BUILD_TYPE is not defined.

### Platform and Versions

- **Operating System**: Windows 10
- **CMake Version**: 3.17.3
- **VSCode Version**: 1.45.1
- **CMake Tools Extension Version**: 1.4.0
- **Compiler/Toolchain**: Visual C++ 2019

### Other Notes/Information

Looking in the project's build directory's CMakeCache.txt file, CMAKE_BUILD_TYPE is not included. When I use Visual Studio 2019, the project behaves as expected and CMAKE_BUILD_TYPE is included in the CMakeCache.txt file.

Start by reproducing the configured Debug project on Windows 10 with CMake Tools 1.4.0 and inspect the project's build directory's CMakeCache.txt. Compare the extension's behavior with Visual Studio 2019, then trace the configuration path that handles the selected build type; done means the expected build-type value is represented consistently in the cache or the documented behavior is clarified.

Written by the indexing model from the issue text.