threadpool: cmake: fix: Win Vista+ ThreadPool unused w/ Ninja generator

Author: sergio-nsk

CMakeLists.txt

@@ -128,7 +128,7 @@ if(WIN32)
         endif()
     endif()
 
-    if(CMAKE_VS_WINDOWS_TARGET_PLATFORM_VERSION GREATER_EQUAL 6.1)
+    if(CMAKE_VS_WINDOWS_TARGET_PLATFORM_VERSION GREATER_EQUAL 6.1 OR CMAKE_SYSTEM_VERSION GREATER_EQUAL 6.1)
         list(APPEND PROXYRES_SRCS
             threadpool_winvista.c)
     else()