$ cmake -DCMAKE_BUILD_TYPE=Release  -DCMAKE_INSTALL_PREFIX=/usr/local  -DCMAKE_CXX_FLAGS=-DMONGOC_HAVE_SSL=1.. &&     make 

[ 22%] Building CXX object src/mongocxx/CMakeFiles/mongocxx.dir/bulk_write.cpp.o
[ 22%] Building CXX object src/mongocxx/CMakeFiles/mongocxx.dir/client.cpp.o
In file included from /mongo-cxx-driver/src/mongocxx/client.cpp:26:0:
/mongo-cxx-driver/src/mongocxx/private/ssl.hpp: In function 'mongoc_ssl_opt_t mongocxx::v_noabi::options::make_ssl_opts(const mongocxx::v_noabi::options::ssl&)':
/mongo-cxx-driver/src/mongocxx/private/ssl.hpp:30:45: error: 'const value_type' has no member named 'c_str'
         out.pem_file = ssl_opts.pem_file()->c_str();
                                             ^
/mongo-cxx-driver/src/mongocxx/private/ssl.hpp:33:48: error: 'const value_type' has no member named 'c_str'
         out.pem_pwd = ssl_opts.pem_password()->c_str();
                                                ^
/mongo-cxx-driver/src/mongocxx/private/ssl.hpp:36:43: error: 'const value_type' has no member named 'c_str'
         out.ca_file = ssl_opts.ca_file()->c_str();
                                           ^
/mongo-cxx-driver/src/mongocxx/private/ssl.hpp:39:41: error: 'const value_type' has no member named 'c_str'
         out.ca_dir = ssl_opts.ca_dir()->c_str();
                                         ^
/mongo-cxx-driver/src/mongocxx/private/ssl.hpp:42:45: error: 'const value_type' has no member named 'c_str'
         out.crl_file = ssl_opts.crl_file()->c_str();
                                             ^
src/mongocxx/CMakeFiles/mongocxx.dir/build.make:86: recipe for target 'src/mongocxx/CMakeFiles/mongocxx.dir/client.cpp.o' failed