docs: meson fails with undefined references when building documentation
The latest tarball, 2.63.92 (and in some previous unstable releases), when building the documentation with Meson I get:
[ 57s] Building documentation for libsoup-2.4
[ 57s] ERROR:
[ 57s] Error in gtkdoc helper script:
[ 57s]
[ 57s] ERROR: 'gtkdoc-scangobj' failed with status 1
[ 57s] /usr/lib64/gcc/x86_64-suse-linux/8/../../../../x86_64-suse-linux/bin/ld: libsoup-2.4-scan.o: in function `get_object_types':
[ 57s] /home/abuild/rpmbuild/BUILD/libsoup-2.63.92/build/libsoup-2.4-scan.c:59: undefined reference to `soup_address_get_type'
[ 57s] /usr/lib64/gcc/x86_64-suse-linux/8/../../../../x86_64-suse-linux/bin/ld: /home/abuild/rpmbuild/BUILD/libsoup-2.63.92/build/libsoup-2.4-scan.c:60: undefined reference to `soup_auth_basic_get_type'
[ 57s] /usr/lib64/gcc/x86_64-suse-linux/8/../../../../x86_64-suse-linux/bin/ld: /home/abuild/rpmbuild/BUILD/libsoup-2.63.92/build/libsoup-2.4-scan.c:61: undefined reference to `soup_auth_digest_get_type'
[ 57s] /usr/lib64/gcc/x86_64-suse-linux/8/../../../../x86_64-suse-linux/bin/ld: /home/abuild/rpmbuild/BUILD/libsoup-2.63.92/build/libsoup-2.4-scan.c:62: undefined reference to `soup_auth_domain_basic_get_type'
[ 57s] /usr/lib64/gcc/x86_64-suse-linux/8/../../../../x86_64-suse-linux/bin/ld: /home/abuild/rpmbuild/BUILD/libsoup-2.63.92/build/libsoup-2.4-scan.c:63: undefined reference to `soup_auth_domain_digest_get_type'
[ 57s] /usr/lib64/gcc/x86_64-suse-linux/8/../../../../x86_64-suse-linux/bin/ld: /home/abuild/rpmbuild/BUILD/libsoup-2.63.92/build/libsoup-2.4-scan.c:64: undefined reference to `soup_auth_domain_get_type'
[ 57s] /usr/lib64/gcc/x86_64-suse-linux/8/../../../../x86_64-suse-linux/bin/ld: /home/abuild/rpmbuild/BUILD/libsoup-2.63.92/build/libsoup-2.4-scan.c:65: undefined reference to `soup_auth_get_type'
[ 57s] /usr/lib64/gcc/x86_64-suse-linux/8/../../../../x86_64-suse-linux/bin/ld: /home/abuild/rpmbuild/BUILD/libsoup-2.63.92/build/libsoup-2.4-scan.c:66: undefined reference to `soup_auth_manager_get_type'
[ 57s] /usr/lib64/gcc/x86_64-suse-linux/8/../../../../x86_64-suse-linux/bin/ld: /home/abuild/rpmbuild/BUILD/libsoup-2.63.92/build/libsoup-2.4-scan.c:67: undefined reference to `soup_auth_negotiate_get_type'
[ 57s] /usr/lib64/gcc/x86_64-suse-linux/8/../../../../x86_64-suse-linux/bin/ld: /home/abuild/rpmbuild/BUILD/libsoup-2.63.92/build/libsoup-2.4-scan.c:68: undefined reference to `soup_auth_ntlm_get_type'
[ 57s] /usr/lib64/gcc/x86_64-suse-linux/8/../../../../x86_64-suse-linux/bin/ld: /home/abuild/rpmbuild/BUILD/libsoup-2.63.92/build/libsoup-2.4-scan.c:69: undefined reference to `soup_buffer_get_type'
[ 57s] /usr/lib64/gcc/x86_64-suse-linux/8/../../../../x86_64-suse-linux/bin/ld: /home/abuild/rpmbuild/BUILD/libsoup-2.63.92/build/libsoup-2.4-scan.c:70: undefined reference to `soup_cache_get_type'
[ 57s] /usr/lib64/gcc/x86_64-suse-linux/8/../../../../x86_64-suse-linux/bin/ld: /home/abuild/rpmbuild/BUILD/libsoup-2.63.92/build/libsoup-2.4-scan.c:71: undefined reference to `soup_client_context_get_type'
[ 57s] /usr/lib64/gcc/x86_64-suse-linux/8/../../../../x86_64-suse-linux/bin/ld: /home/abuild/rpmbuild/BUILD/libsoup-2.63.92/build/libsoup-2.4-scan.c:72: undefined reference to `soup_content_decoder_get_type'
[ 57s] /usr/lib64/gcc/x86_64-suse-linux/8/../../../../x86_64-suse-linux/bin/ld: /home/abuild/rpmbuild/BUILD/libsoup-2.63.92/build/libsoup-2.4-scan.c:73: undefined reference to `soup_content_sniffer_get_type'
[ 57s] /usr/lib64/gcc/x86_64-suse-linux/8/../../../../x86_64-suse-linux/bin/ld: /home/abuild/rpmbuild/BUILD/libsoup-2.63.92/build/libsoup-2.4-scan.c:74: undefined reference to `soup_cookie_get_type'
[ 57s] /usr/lib64/gcc/x86_64-suse-linux/8/../../../../x86_64-suse-linux/bin/ld: /home/abuild/rpmbuild/BUILD/libsoup-2.63.92/build/libsoup-2.4-scan.c:75: undefined reference to `soup_cookie_jar_db_get_type'
[ 57s] /usr/lib64/gcc/x86_64-suse-linux/8/../../../../x86_64-suse-linux/bin/ld: /home/abuild/rpmbuild/BUILD/libsoup-2.63.92/build/libsoup-2.4-scan.c:76: undefined reference to `soup_cookie_jar_get_type'
[ 57s] /usr/lib64/gcc/x86_64-suse-linux/8/../../../../x86_64-suse-linux/bin/ld: /home/abuild/rpmbuild/BUILD/libsoup-2.63.92/build/libsoup-2.4-scan.c:77: undefined reference to `soup_cookie_jar_text_get_type'
[ 57s] /usr/lib64/gcc/x86_64-suse-linux/8/../../../../x86_64-suse-linux/bin/ld: /home/abuild/rpmbuild/BUILD/libsoup-2.63.92/build/libsoup-2.4-scan.c:78: undefined reference to `soup_date_get_type'
[ 57s] /usr/lib64/gcc/x86_64-suse-linux/8/../../../../x86_64-suse-linux/bin/ld: /home/abuild/rpmbuild/BUILD/libsoup-2.63.92/build/libsoup-2.4-scan.c:79: undefined reference to `soup_logger_get_type'
[ 57s] /usr/lib64/gcc/x86_64-suse-linux/8/../../../../x86_64-suse-linux/bin/ld: /home/abuild/rpmbuild/BUILD/libsoup-2.63.92/build/libsoup-2.4-scan.c:80: undefined reference to `soup_message_body_get_type'
[ 57s] /usr/lib64/gcc/x86_64-suse-linux/8/../../../../x86_64-suse-linux/bin/ld: /home/abuild/rpmbuild/BUILD/libsoup-2.63.92/build/libsoup-2.4-scan.c:81: undefined reference to `soup_message_get_type'
[ 57s] /usr/lib64/gcc/x86_64-suse-linux/8/../../../../x86_64-suse-linux/bin/ld: /home/abuild/rpmbuild/BUILD/libsoup-2.63.92/build/libsoup-2.4-scan.c:82: undefined reference to `soup_message_headers_get_type'
[ 57s] /usr/lib64/gcc/x86_64-suse-linux/8/../../../../x86_64-suse-linux/bin/ld: /home/abuild/rpmbuild/BUILD/libsoup-2.63.92/build/libsoup-2.4-scan.c:83: undefined reference to `soup_multipart_get_type'
[ 57s] /usr/lib64/gcc/x86_64-suse-linux/8/../../../../x86_64-suse-linux/bin/ld: /home/abuild/rpmbuild/BUILD/libsoup-2.63.92/build/libsoup-2.4-scan.c:84: undefined reference to `soup_multipart_input_stream_get_type'
[ 57s] /usr/lib64/gcc/x86_64-suse-linux/8/../../../../x86_64-suse-linux/bin/ld: /home/abuild/rpmbuild/BUILD/libsoup-2.63.92/build/libsoup-2.4-scan.c:85: undefined reference to `soup_proxy_resolver_default_get_type'
[ 57s] /usr/lib64/gcc/x86_64-suse-linux/8/../../../../x86_64-suse-linux/bin/ld: /home/abuild/rpmbuild/BUILD/libsoup-2.63.92/build/libsoup-2.4-scan.c:86: undefined reference to `soup_request_data_get_type'
[ 57s] /usr/lib64/gcc/x86_64-suse-linux/8/../../../../x86_64-suse-linux/bin/ld: /home/abuild/rpmbuild/BUILD/libsoup-2.63.92/build/libsoup-2.4-scan.c:87: undefined reference to `soup_request_file_get_type'
[ 57s] /usr/lib64/gcc/x86_64-suse-linux/8/../../../../x86_64-suse-linux/bin/ld: /home/abuild/rpmbuild/BUILD/libsoup-2.63.92/build/libsoup-2.4-scan.c:88: undefined reference to `soup_request_get_type'
[ 57s] /usr/lib64/gcc/x86_64-suse-linux/8/../../../../x86_64-suse-linux/bin/ld: /home/abuild/rpmbuild/BUILD/libsoup-2.63.92/build/libsoup-2.4-scan.c:89: undefined reference to `soup_request_http_get_type'
[ 57s] /usr/lib64/gcc/x86_64-suse-linux/8/../../../../x86_64-suse-linux/bin/ld: /home/abuild/rpmbuild/BUILD/libsoup-2.63.92/build/libsoup-2.4-scan.c:90: undefined reference to `soup_server_get_type'
[ 57s] /usr/lib64/gcc/x86_64-suse-linux/8/../../../../x86_64-suse-linux/bin/ld: /home/abuild/rpmbuild/BUILD/libsoup-2.63.92/build/libsoup-2.4-scan.c:91: undefined reference to `soup_session_async_get_type'
[ 57s] /usr/lib64/gcc/x86_64-suse-linux/8/../../../../x86_64-suse-linux/bin/ld: /home/abuild/rpmbuild/BUILD/libsoup-2.63.92/build/libsoup-2.4-scan.c:92: undefined reference to `soup_session_feature_get_type'
[ 57s] /usr/lib64/gcc/x86_64-suse-linux/8/../../../../x86_64-suse-linux/bin/ld: /home/abuild/rpmbuild/BUILD/libsoup-2.63.92/build/libsoup-2.4-scan.c:93: undefined reference to `soup_session_get_type'
[ 57s] /usr/lib64/gcc/x86_64-suse-linux/8/../../../../x86_64-suse-linux/bin/ld: /home/abuild/rpmbuild/BUILD/libsoup-2.63.92/build/libsoup-2.4-scan.c:94: undefined reference to `soup_session_sync_get_type'
[ 57s] /usr/lib64/gcc/x86_64-suse-linux/8/../../../../x86_64-suse-linux/bin/ld: /home/abuild/rpmbuild/BUILD/libsoup-2.63.92/build/libsoup-2.4-scan.c:95: undefined reference to `soup_socket_get_type'
[ 57s] /usr/lib64/gcc/x86_64-suse-linux/8/../../../../x86_64-suse-linux/bin/ld: /home/abuild/rpmbuild/BUILD/libsoup-2.63.92/build/libsoup-2.4-scan.c:96: undefined reference to `soup_uri_get_type'
[ 57s] /usr/lib64/gcc/x86_64-suse-linux/8/../../../../x86_64-suse-linux/bin/ld: /home/abuild/rpmbuild/BUILD/libsoup-2.63.92/build/libsoup-2.4-scan.c:97: undefined reference to `soup_websocket_connection_get_type'
[ 57s] collect2: error: ld returned 1 exit status
[ 57s] 2018-08-29 23:34:21,426:scangobj.py:execute_command:1196:WARNING:Linking scanner failed: 1, command: cc libsoup-2.4-scan.o -O2 -Wall -D_FORTIFY_SOURCE=2 -fstack-protector-strong -funwind-tables -fasynchronous-unwind-tables -fstack-clash-protection -g -lglib-2.0 -lgobject-2.0 -lgio-2.0 -lxml2 -o libsoup-2.4-scan