CXX-2726 do not override CMAKE_BUILD_TYPE for multi-config generator (#1006)

* do not override CMAKE_BUILD_TYPE for multi-config generator

* remove CMAKE_BUILD_TYPE from Windows install instructions

CMAKE_BUILT_TYPE is ignored for multi-config generators like Visual Studio

* specify `--config` in Windows install instructions

Author: kevinAlbs

CMakeLists.txt

@@ -250,7 +250,10 @@ if(BUILD_VERSION STREQUAL "0.0.0")
     endif()
 endif()
 
-if(NOT CMAKE_BUILD_TYPE)
+get_property(isMultiConfig GLOBAL PROPERTY GENERATOR_IS_MULTI_CONFIG)
+
+if(NOT CMAKE_BUILD_TYPE AND NOT isMultiConfig)
+    # Do not override CMAKE_BUILD_TYPE if generator is multi config. CMAKE_BUILD_TYPE is ignored for multi-config generators.
     message(STATUS "No build type selected, default is Release")
     set(CMAKE_BUILD_TYPE "Release")
 endif()

docs/content/mongocxx-v3/installation/windows.md

@@ -104,18 +104,17 @@ To build versions 3.7.0 and older without a C++17 polyfill, it is necessary to c
 
 ```sh
 cmake ..                                            \
-    -DCMAKE_BUILD_TYPE=Release                      \
     -DLIBMONGOC_DIR=C:\mongo-c-driver               \
     -DCMAKE_INSTALL_PREFIX=C:\mongo-cxx-driver
 ```
 
 ### Step 4: Build and install the driver
 
-Build and install the driver:
+Build and install the driver. Use `--config` to select a build configuration (e.g. `Debug`, `RelWithDebInfo`, `Release`):
 
 ```sh
-cmake --build .
-cmake --build . --target install
+cmake --build . --config RelWithDebInfo
+cmake --build . --target install --config RelWithDebInfo
 ```
 
 The driver can be uninstalled at a later time in one of two ways.  First,