fix Windows cmake for BUILD_SEPARATE_OPS

Author: xuhancn

src/BuildOnWindows.cmake

@@ -8,8 +8,6 @@ macro(setup_common_libraries)
     torch_xpu_ops
     STATIC
     ${ATen_XPU_CPP_SRCS})
-  set(PATH_TO_TORCH_XPU_OPS_ATEN_LIB \"torch_xpu_ops_aten.dll\")
-  target_compile_options(torch_xpu_ops PRIVATE -DPATH_TO_TORCH_XPU_OPS_ATEN_LIB=${PATH_TO_TORCH_XPU_OPS_ATEN_LIB})
 
   add_library(
     torch_xpu_ops_aten
@@ -33,6 +31,7 @@ if(BUILD_SEPARATE_OPS)
       ${sycl_lib}
       SHARED
       SYCL_SOURCES ${sycl_src})
+    target_compile_definitions(${sycl_lib} PRIVATE TORCH_XPU_BUILD_MAIN_LIB)
     target_link_libraries(torch_xpu_ops_aten PUBLIC ${sycl_lib})
     list(APPEND TORCH_XPU_OPS_LIBRARIES ${sycl_lib})