Android: Fix build with NDK 27

`NDK_PROC_*_ABI` and `NDK_ARCH_*_ABI` were removed in the Android
NDK 27 but will be reintroduced in the Android NDK 27b:

* https://github.com/android/ndk/issues/2049
* https://android-review.googlesource.com/c/platform/ndk/+/3196345

Both are only used when `CMAKE_ANDROID_ARCH_ABI` is NOT given. But
currently the existence is also checked when `CMAKE_ANDROID_ARCH_ABI`
is given. So we move the checks to the position they are required.

Modules/Platform/Android-Determine.cmake

@@ -375,21 +375,21 @@ endif()
 if(CMAKE_ANDROID_ARCH_ABI AND NOT DEFINED "NDK_ABI_${CMAKE_ANDROID_ARCH_ABI}_PROC")
   message(FATAL_ERROR "Android: Unknown ABI CMAKE_ANDROID_ARCH_ABI='${CMAKE_ANDROID_ARCH_ABI}'.")
 endif()
-if(CMAKE_SYSTEM_PROCESSOR AND NOT DEFINED "NDK_PROC_${CMAKE_SYSTEM_PROCESSOR}_ABI")
-  message(FATAL_ERROR "Android: Unknown processor CMAKE_SYSTEM_PROCESSOR='${CMAKE_SYSTEM_PROCESSOR}'.")
-endif()
-if(_ANDROID_SYSROOT_ARCH AND NOT DEFINED "NDK_ARCH_${_ANDROID_SYSROOT_ARCH}_ABI")
-  message(FATAL_ERROR
-    "Android: Unknown architecture '${_ANDROID_SYSROOT_ARCH}' specified in CMAKE_SYSROOT:\n"
-    "  ${CMAKE_SYSROOT}"
-    )
-endif()
 
 # Select an ABI.
 if(NOT CMAKE_ANDROID_ARCH_ABI)
   if(CMAKE_SYSTEM_PROCESSOR)
+    if(NOT DEFINED "NDK_PROC_${CMAKE_SYSTEM_PROCESSOR}_ABI")
+      message(FATAL_ERROR "Android: Unknown processor CMAKE_SYSTEM_PROCESSOR='${CMAKE_SYSTEM_PROCESSOR}'.")
+    endif()
     set(CMAKE_ANDROID_ARCH_ABI "${NDK_PROC_${CMAKE_SYSTEM_PROCESSOR}_ABI}")
   elseif(_ANDROID_SYSROOT_ARCH)
+    if(NOT DEFINED "NDK_ARCH_${_ANDROID_SYSROOT_ARCH}_ABI")
+      message(FATAL_ERROR
+        "Android: Unknown architecture '${_ANDROID_SYSROOT_ARCH}' specified in CMAKE_SYSROOT:\n"
+        "  ${CMAKE_SYSROOT}"
+        )
+    endif()
     set(CMAKE_ANDROID_ARCH_ABI "${NDK_ARCH_${_ANDROID_SYSROOT_ARCH}_ABI}")
   elseif(_INCLUDED_ABIS)
     # Default to the oldest ARM ABI.