There is more

We have shown how the variable CMAKE_BUILD_TYPE (documented at this link: https://cmake.org/cmake/help/v3.5/variable/CMAKE_BUILD_TYPE.html) defines the configuration of the generated build system. It is often helpful to build a project both in Release and Debug configurations, for example when assessing the effect of compiler optimization levels. For single-configuration generators, such as Unix Makefiles, MSYS Makefiles or Ninja, this requires running CMake twice, that is a full reconfiguration of the project. CMake however also supports multiple-configuration generators. These are usually project files offered by integrated-development environments, most notably Visual Studio and Xcode which can handle more than one configuration simultaneously. The available configuration types for these generators can be tweaked with the CMAKE_CONFIGURATION_TYPES variable which will accept a list of values (documentation available at this link: https://cmake.org/cmake/help/v3.5/variable/CMAKE_CONFIGURATION_TYPES.html).

The following CMake invocation with the Visual Studio:

$ mkdir -p build
$ cd build
$ cmake .. -G"Visual Studio 12 2017 Win64" -D CMAKE_CONFIGURATION_TYPES="Release;Debug"

will generate a build tree for both the Release and Debug configuration. You can then decide which of the two to build by using the --config flag:

$ cmake --build . --config Release