I get this:

In file included from /home/gho/code/pc3-mongo-cxx-driver/src/mongocxx/options/auto_encryption.cpp:15:
In file included from /home/gho/code/pc3-mongo-cxx-driver/src/mongocxx/options/auto_encryption.hpp:17:
In file included from /home/gho/code/pc3-mongo-cxx-driver/src/bsoncxx/document/view_or_value.hpp:17:
In file included from /home/gho/code/pc3-mongo-cxx-driver/src/bsoncxx/document/value.hpp:18:
In file included from /usr/lib/llvm-10/bin/../include/c++/v1/memory:657:
/usr/lib/llvm-10/bin/../include/c++/v1/utility:305:9: error: implicit instantiation of undefined template 'std::_1::basic_string<char, std::1::char_traits<char>, std::_1::allocator<char> >'
_T1 first;
^
/usr/lib/llvm-10/bin/../include/c++/v1/type_traits:3035:38: note: in instantiation of template class 'std::_1::pair<std::1::basic_string<char, std::1::char_traits<char>, std::1::allocator<char> >, std::1::basic_string<char, std::1::char_traits<char>, std::_1::allocator<char> > >' requested here
: public integral_constant<bool, __is_trivially_destructible(_Tp)> {};
^
/usr/lib/llvm-10/bin/../include/c++/v1/optional:538:5: note: in instantiation of template class 'std::_1::is_trivially_destructible<std::1::pair<std::1::basic_string<char, std::1::char_traits<char>, std::1::allocator<char> >, std::1::basic_string<char, std::1::char_traits<char>, std::_1::allocator<char> > > >' requested here
is_trivially_destructible<_Tp>::value &&
^
/usr/lib/llvm-10/bin/../include/c++/v1/optional:585:15: note: in instantiation of default argument for '_optional_move_assign_base<std::1::pair<std::1::basic_string<char, std::1::char_traits<char>, std::1::allocator<char> >, std::1::basic_string<char, std::1::char_traits<char>, std::_1::allocator<char> > > >' required here
: private __optional_move_assign_base<_Tp>
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/gho/code/pc3-mongo-cxx-driver/src/mongocxx/options/auto_encryption.hpp:254:29: note: in instantiation of template class 'std::_1::optional<std::1::pair<std::1::basic_string<char, std::1::char_traits<char>, std::1::allocator<char> >, std::1::basic_string<char, std::1::char_traits<char>, std::_1::allocator<char> > > >' requested here
stdx::optional<ns_pair> _key_vault_namespace;
^
/usr/lib/llvm-10/bin/../include/c++/v1/iosfwd:209:32: note: template is declared here
class _LIBCPP_TEMPLATE_VIS basic_string;
^