Prevent crash on import after GCC 8 builds (#6048)

### Description
Possible fix for #6047 based on
https://stackoverflow.com/questions/33149878/experimentalfilesystem-linker-error/33159746#33159746

### Motivation and Context
I'm not a cmake expert so there may be a better way to do this. This did
allow me to build ONNX 1.16 on RHEL 8.

---------

Signed-off-by: Charles Volzka <cjvolzka@us.ibm.com>
Signed-off-by: Charles Volzka <42243335+cjvolzka@users.noreply.github.com>
Co-authored-by: Thiago Crepaldi <thiago.crepaldi@microsoft.com>
Co-authored-by: G. Ramalingam <grama@microsoft.com>

CMakeLists.txt

@@ -587,6 +587,11 @@ if(BUILD_ONNX_PYTHON)
     target_link_libraries(onnx_cpp2py_export
                           PRIVATE "-Wl,--whole-archive" $<TARGET_FILE:onnx>
                                   "-Wl,--no-whole-archive")
+    # Prevent "undefined symbol: _ZNSt10filesystem7__cxx114path14_M_split_cmptsEv" 
+    # (std::filesystem::__cxx11::path::_M_split_cmpts()) on gcc 8
+    if (CMAKE_CXX_STANDARD EQUAL 17 AND CMAKE_COMPILER_IS_GNUCC AND CMAKE_CXX_COMPILER_VERSION VERSION_LESS 9.0)
+      target_link_libraries(onnx_cpp2py_export PRIVATE "-lstdc++fs")
+    endif()
     set_target_properties(onnx_cpp2py_export
                           PROPERTIES LINK_FLAGS "-Wl,--exclude-libs,ALL")
   endif()