Fix draco building error when import assimp with cmake add_subdirectory #3663

contrib/draco/CMakeLists.txt

@@ -10,7 +10,7 @@ endif()
 
 set(draco_root "${CMAKE_CURRENT_SOURCE_DIR}")
 set(draco_src_root "${draco_root}/src/draco")
-set(draco_build "${CMAKE_BINARY_DIR}")
+set(draco_build "${Assimp_BINARY_DIR}")
 
 if("${draco_root}" STREQUAL "${draco_build}")
   message(