./configure --with-gnutls=no --with-openssl=yes
make

[snip]
gcc -DHAVE_CONFIG_H -I. -I../..  -I../../src/include -DDATA_DIR=\"../../src/datadir/\" -DCPU_COUNT=8    -g -O2 -fno-strict-aliasing -MT benchmark-benchmark.o -MD -MP -MF .deps/benchmark-benchmark.Tpo -c -o benchmark-benchmark.o `test -f 'benchmark.c' || echo './'`benchmark.c
mv -f .deps/benchmark-benchmark.Tpo .deps/benchmark-benchmark.Po
/bin/bash ../../libtool  --tag=CC   --mode=link gcc   -g -O2 -fno-strict-aliasing   -o benchmark benchmark-benchmark.o ../../src/microhttpd/libmicrohttpd.la 
libtool: link: gcc -g -O2 -fno-strict-aliasing -o .libs/benchmark benchmark-benchmark.o  ../../src/microhttpd/.libs/libmicrohttpd.so -pthread
../../src/microhttpd/.libs/libmicrohttpd.so: undefined reference to `MHD_TLS_del_session'
../../src/microhttpd/.libs/libmicrohttpd.so: undefined reference to `MHD_TLS_del_context'
../../src/microhttpd/.libs/libmicrohttpd.so: undefined reference to `MHD_TLS_create_context'
../../src/microhttpd/.libs/libmicrohttpd.so: undefined reference to `MHD_TLS_set_context_client_certificate_mode'
../../src/microhttpd/.libs/libmicrohttpd.so: undefined reference to `MHD_TLS_set_context_certificate_cb'
../../src/microhttpd/.libs/libmicrohttpd.so: undefined reference to `MHD_TLS_session_wants_write'
../../src/microhttpd/.libs/libmicrohttpd.so: undefined reference to `MHD_set_https_callbacks'
../../src/microhttpd/.libs/libmicrohttpd.so: undefined reference to `MHD_TLS_global_deinit'
../../src/microhttpd/.libs/libmicrohttpd.so: undefined reference to `MHD_tls_connection_shutdown'
../../src/microhttpd/.libs/libmicrohttpd.so: undefined reference to `MHD_TLS_session_read'
../../src/microhttpd/.libs/libmicrohttpd.so: undefined reference to `MHD_TLS_get_session_protocol_version'
../../src/microhttpd/.libs/libmicrohttpd.so: undefined reference to `MHD_TLS_get_specific_session'
../../src/microhttpd/.libs/libmicrohttpd.so: undefined reference to `MHD_TLS_session_close'
../../src/microhttpd/.libs/libmicrohttpd.so: undefined reference to `MHD_TLS_session_read_pending'
../../src/microhttpd/.libs/libmicrohttpd.so: undefined reference to `MHD_run_tls_handshake_'
../../src/microhttpd/.libs/libmicrohttpd.so: undefined reference to `MHD_TLS_set_context_trust_certificate'
../../src/microhttpd/.libs/libmicrohttpd.so: undefined reference to `MHD_TLS_get_session_cipher_algorithm'
../../src/microhttpd/.libs/libmicrohttpd.so: undefined reference to `MHD_TLS_session_wants_read'
../../src/microhttpd/.libs/libmicrohttpd.so: undefined reference to `MHD_TLS_set_context_cipher_priorities'
../../src/microhttpd/.libs/libmicrohttpd.so: undefined reference to `MHD_TLS_lookup_engine'
../../src/microhttpd/.libs/libmicrohttpd.so: undefined reference to `MHD_TLS_create_session'
../../src/microhttpd/.libs/libmicrohttpd.so: undefined reference to `MHD_TLS_engine_has_feature'
../../src/microhttpd/.libs/libmicrohttpd.so: undefined reference to `MHD_TLS_set_context_dh_params'
../../src/microhttpd/.libs/libmicrohttpd.so: undefined reference to `MHD_TLS_global_init'
../../src/microhttpd/.libs/libmicrohttpd.so: undefined reference to `MHD_TLS_set_context_certificate'
../../src/microhttpd/.libs/libmicrohttpd.so: undefined reference to `MHD_TLS_session_write'
collect2: error: ld returned 1 exit status
Makefile:734: recipe for target 'benchmark' failed
make[4]: *** [benchmark] Error 1
make[4]: Leaving directory '/home/silvioprog/dev/git/libmicrohttpd2/src/examples'
Makefile:938: recipe for target 'all-recursive' failed
make[3]: *** [all-recursive] Error 1
make[3]: Leaving directory '/home/silvioprog/dev/git/libmicrohttpd2/src/examples'
Makefile:418: recipe for target 'all-recursive' failed
make[2]: *** [all-recursive] Error 1
make[2]: Leaving directory '/home/silvioprog/dev/git/libmicrohttpd2/src'
Makefile:549: recipe for target 'all-recursive' failed
make[1]: *** [all-recursive] Error 1
make[1]: Leaving directory '/home/silvioprog/dev/git/libmicrohttpd2'
Makefile:454: recipe for target 'all' failed
make: *** [all] Error 2

./configure --with-openssl=no
make
[snip]
libtool: compile:  gcc -DHAVE_CONFIG_H -I. -I../.. -I../../src/include -I../../src/microhttpd -I/usr/include/p11-kit-1 -DBUILDING_MHD_LIB=1 -fvisibility=hidden -pthread -I/usr/include/p11-kit-1 -g -O2 -fno-strict-aliasing -MT libmicrohttpd_la-connection.lo -MD -MP -MF .deps/libmicrohttpd_la-connection.Tpo -c connection.c  -fPIC -DPIC -o .libs/libmicrohttpd_la-connection.o
In file included from internal.h:32:0,
                 from connection.c:28:
tls.h:493:31: error: field ‘gnutls’ has incomplete type
     struct MHD_GnuTLS_Context gnutls;
                               ^
tls.h:529:31: error: field ‘gnutls’ has incomplete type
     struct MHD_GnuTLS_Session gnutls;
                               ^
connection.c: In function ‘MHD_get_connection_info’:
connection.c:3764:28: warning: implicit declaration of function ‘gnutls_cipher_get’ [-Wimplicit-function-declaration]
       connection->cipher = gnutls_cipher_get (connection->tls_session->d.gnutls
                            ^
connection.c:3775:30: warning: implicit declaration of function ‘gnutls_protocol_get_version’ [-Wimplicit-function-declaration]
       connection->protocol = gnutls_protocol_get_version (connection->tls_sessi
                              ^
Makefile:1182: recipe for target 'libmicrohttpd_la-connection.lo' failed
make[3]: *** [libmicrohttpd_la-connection.lo] Error 1
make[3]: Leaving directory '/home/silvioprog/dev/git/libmicrohttpd2/src/microhttpd'
Makefile:418: recipe for target 'all-recursive' failed
make[2]: *** [all-recursive] Error 1
make[2]: Leaving directory '/home/silvioprog/dev/git/libmicrohttpd2/src'
Makefile:549: recipe for target 'all-recursive' failed
make[1]: *** [all-recursive] Error 1
make[1]: Leaving directory '/home/silvioprog/dev/git/libmicrohttpd2'
Makefile:454: recipe for target 'all' failed
make: *** [all] Error 2