Android/Clang: Tolerate undefined CMAKE_ANDROID_NDK_VERSION

The previous fix for #21772, commit 005e2cdfb0 (Android: Do not use gold
for ndk >= r22, 2021-02-26, v3.20.0-rc3~1^2), doesn't work with typical
android toolchain file, like this one:

    https://android.googlesource.com/platform/ndk/+/master/build/cmake/android-legacy.toolchain.cmake

The condition fails to work when CMAKE_ANDROID_NDK_VERSION is undefined:
second part evaluates to true, although ndk version is not known.

I've encountered following environment where CMAKE_ANDROID_NDK_VERSION
is used without definition:

* Build uses android toolchain file, which sets CMAKE_SYSTEM_VERSION=1
  and doesn't set CMAKE_ANDROID_NDK_VERSION.
* Code in Platform/Android-Determine.cmake exits early when it detects
  toolchain usage (via value CMAKE_SYSTEM_VERSION=1). This file is the
  only place in cmake modules where variable CMAKE_ANDROID_NDK_VERSION
  is set, and by early return we skip this definition.

Modules/Compiler/Clang.cmake

@@ -80,7 +80,7 @@ else()
       set(CMAKE_${lang}_COMPILE_OPTIONS_IPO "-flto")
     endif()
 
-    if(ANDROID AND NOT CMAKE_ANDROID_NDK_VERSION VERSION_GREATER_EQUAL "22")
+    if(ANDROID AND CMAKE_ANDROID_NDK_VERSION VERSION_LESS "22")
       # https://github.com/android-ndk/ndk/issues/242
       set(CMAKE_${lang}_LINK_OPTIONS_IPO "-fuse-ld=gold")
     endif()