Lld-link: error: undefined symbol

Hi: I compiled an opencv by vs2017 and then want to use this library under pdfium project( it use clang) got following error.
lld-link: error: undefined symbol: bool __cdecl cv::imencode(class cv::String const &, class cv::_InputArray const &, class std::__1::vector<unsigned char, class std::__1::allocator> &, class std::__1::vector<int, class std::__1::allocator> const &)