Android: Use NDK_KNOWN_DEVICE_ABI{32,64}S instead of NDK_DEFAULT_ABIS

Revise logic from commit 1ab574a0f4 (Android: Add support for NDK r22,
2020-10-07, v3.19.0-rc1~18^2) that loads ABI tables from the NDK.

`NDK_DEFAULT_ABIS` means the abis to build by default.
Use `NDK_KNOWN_DEVICE_ABI{32,64}S` instead.

In practise they have never been different. Fix to make it more precise.

Modules/Platform/Android-Determine.cmake

@@ -202,8 +202,13 @@ if(NOT CMAKE_ANDROID_NDK AND NOT CMAKE_ANDROID_STANDALONE_TOOLCHAIN)
 endif()
 
 if(CMAKE_ANDROID_NDK)
-  # NDK >= 18 has abis.cmake and platforms.cmake.
+  # NDK >= 18 has platforms.cmake. It provides:
+  #   NDK_MIN_PLATFORM_LEVEL
+  #   NDK_MAX_PLATFORM_LEVEL
   include("${CMAKE_ANDROID_NDK}/build/cmake/platforms.cmake" OPTIONAL RESULT_VARIABLE _INCLUDED_PLATFORMS)
+  # NDK >= 18 has abis.cmake. It provides:
+  #   NDK_KNOWN_DEVICE_ABI32S
+  #   NDK_KNOWN_DEVICE_ABI64S
   include("${CMAKE_ANDROID_NDK}/build/cmake/abis.cmake" OPTIONAL RESULT_VARIABLE _INCLUDED_ABIS)
 endif()
 
@@ -241,6 +246,10 @@ else()
   set(CMAKE_ANDROID_NDK_TOOLCHAIN_UNIFIED "")
 endif()
 
+if(_INCLUDED_ABIS)
+  set(_ANDROID_KNOWN_ABIS ${NDK_KNOWN_DEVICE_ABI32S} ${NDK_KNOWN_DEVICE_ABI64S})
+endif()
+
 # https://developer.android.com/ndk/guides/abis.html
 
 set(_ANDROID_ABI_arm64-v8a_PROC     "aarch64")
@@ -307,7 +316,7 @@ if(NOT CMAKE_ANDROID_ARCH_ABI)
   elseif(_INCLUDED_ABIS)
     # Default to the oldest ARM ABI.
     foreach(abi armeabi armeabi-v7a arm64-v8a)
-      if("${abi}" IN_LIST NDK_DEFAULT_ABIS)
+      if("${abi}" IN_LIST _ANDROID_KNOWN_ABIS)
         set(CMAKE_ANDROID_ARCH_ABI "${abi}")
         break()
       endif()
@@ -353,10 +362,10 @@ if(NOT CMAKE_ANDROID_ARCH_ABI)
     endif()
   endif()
 endif()
-if(_INCLUDED_ABIS AND NOT CMAKE_ANDROID_ARCH_ABI IN_LIST NDK_DEFAULT_ABIS)
+if(_INCLUDED_ABIS AND NOT CMAKE_ANDROID_ARCH_ABI IN_LIST _ANDROID_KNOWN_ABIS)
   message(FATAL_ERROR
     "Android: ABI '${CMAKE_ANDROID_ARCH_ABI}' is not supported by the NDK.\n"
-    "Supported ABIS: ${NDK_DEFAULT_ABIS}."
+    "Supported ABIS: ${_ANDROID_KNOWN_ABIS}."
   )
 endif()
 set(CMAKE_ANDROID_ARCH "${_ANDROID_ABI_${CMAKE_ANDROID_ARCH_ABI}_ARCH}")