fixed parallel build under Windows

CMakeLists.txt

@@ -198,12 +198,14 @@ if(MSVC)
         endforeach(flag_var)
     endif(BUILD_WITH_STATIC_CRT)
 
+	if(NOT ${CMAKE_MAJOR_VERSION}.${CMAKE_MINOR_VERSION} LESS 2.8 AND NOT ${CMAKE_MINOR_VERSION}.${CMAKE_PATCH_VERSION} LESS 8.6)
 		include(ProcessorCount)
 		ProcessorCount(N)
 		if(NOT N EQUAL 0)
 			SET(CMAKE_C_FLAGS   "${CMAKE_C_FLAGS}   /MP${N} ")
 			SET(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /MP${N} ")
 		endif()
+	endif()
 
     if(NOT BUILD_WITH_DEBUG_INFO)
         string(REPLACE "/debug" "" CMAKE_EXE_LINKER_FLAGS_DEBUG "${CMAKE_EXE_LINKER_FLAGS_DEBUG}")