Fix build on gcc-based architectures:
/usr/local/lib/libpoppler.so: undefined reference to `std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >::compare(unsigned long, unsigned long, char const*, unsigned long) const@GLIBCXX_3.4.21'
Approved by: portmgr (tier-2 blanket)