CMakeFindPackageMode: Fix Debian multiarch default guess (#15250)

In commit v2.8.6~102^2~18 (Better support for lib64 and Debian
multiarch, 2011-07-14) variable names "..._LANGUAGE_ARCHITECTURE" were
set instead of the correct "..._LIBRARY_ARCHITECTURE".  Fix this typo
and also set the language-independent variable
CMAKE_LIBRARY_ARCHITECTURE.

Modules/CMakeFindPackageMode.cmake

@@ -102,15 +102,18 @@ if(UNIX)
 
   # guess Debian multiarch if it has not been set:
   if(EXISTS /etc/debian_version)
-    if(NOT CMAKE_${LANGUAGE}_LANGUAGE_ARCHITECTURE )
+    if(NOT CMAKE_${LANGUAGE}_LIBRARY_ARCHITECTURE )
       file(GLOB filesInLib RELATIVE /lib /lib/*-linux-gnu* )
       foreach(file ${filesInLib})
         if("${file}" MATCHES "${CMAKE_LIBRARY_ARCHITECTURE_REGEX}")
-          set(CMAKE_${LANGUAGE}_LANGUAGE_ARCHITECTURE ${file})
+          set(CMAKE_${LANGUAGE}_LIBRARY_ARCHITECTURE ${file})
           break()
         endif()
       endforeach()
     endif()
+    if(NOT CMAKE_LIBRARY_ARCHITECTURE)
+      set(CMAKE_LIBRARY_ARCHITECTURE ${CMAKE_${LANGUAGE}_LIBRARY_ARCHITECTURE})
+    endif()
   endif()
 
 endif()