Help: Document CMAKE_ANDROID_NDK_VERSION variable

Help/manual/cmake-toolchains.7.rst

@@ -359,6 +359,10 @@ CMake uses the following steps to select one of the environments:
 * Else, an error diagnostic will be issued that neither the NDK or
   Standalone Toolchain can be found.
 
+.. versionadded:: 3.20
+  If an Android NDK is selected, its version number is reported
+  in the :variable:`CMAKE_ANDROID_NDK_VERSION` variable.
+
 .. _`Cross Compiling for Android with the NDK`:
 
 Cross Compiling for Android with the NDK

Help/manual/cmake-variables.7.rst

@@ -278,6 +278,7 @@ Variables that Describe the System
    /variable/ANDROID
    /variable/APPLE
    /variable/BORLAND
+   /variable/CMAKE_ANDROID_NDK_VERSION
    /variable/CMAKE_CL_64
    /variable/CMAKE_COMPILER_2005
    /variable/CMAKE_HOST_APPLE

Help/release/3.20.rst

@@ -73,6 +73,9 @@ Platforms
   - The default :variable:`CMAKE_BUILD_TYPE` for Android is
     now ``RelWithDebInfo``.
 
+  - The :variable:`CMAKE_ANDROID_NDK_VERSION` variable was added to
+    report the version of the NDK.
+
 File-Based API
 --------------
 

Help/variable/CMAKE_ANDROID_NDK_VERSION.rst

+CMAKE_ANDROID_NDK_VERSION
+-------------------------
+
+.. versionadded:: 3.20
+
+When :ref:`Cross Compiling for Android with the NDK` and using an
+Android NDK version 11 or higher, this variable is provided by
+CMake to report the NDK version number.