testing libs compiled even without --with-gtest

Looks like some of test related libs are compiled even if unit tests are not enabled:

make[5]: Entering directory '/home/wlodek/kea/src/bin/dhcp4'
  CXX      dhcp4_srv.lo
  CXX      dhcp4to6_ipc.lo
  CXX      client_handler.lo
  CXX      dhcp4_lexer.lo
  CXX      dhcp4_parser.lo
  CXX      parser_context.lo
  CXX      dhcp4_messages.lo
  CXXLD    libdhcp4.la
  CXXLD    kea-dhcp4
make[5]: Leaving directory '/home/wlodek/kea/src/bin/dhcp4'
Making all in tests
make[5]: Entering directory '/home/wlodek/kea/src/bin/dhcp4/tests'
Making all in .
make[6]: Entering directory '/home/wlodek/kea/src/bin/dhcp4/tests'
  CXX      libco1_la-callout_library_1.lo
  CXX      libco2_la-callout_library_2.lo
  CXX      libco3_la-callout_library_3.lo
  CXXLD    libco2.la
  CXXLD    libco1.la
  CXXLD    libco3.la
make[6]: Leaving directory '/home/wlodek/kea/src/bin/dhcp4/tests'
make[5]: Leaving directory '/home/wlodek/kea/src/bin/dhcp4/tests'
make[4]: Leaving directory '/home/wlodek/kea/src/bin/dhcp4'
Making all in dhcp6
make[4]: Entering directory '/home/wlodek/kea/src/bin/dhcp6'
Making all in .
make[5]: Entering directory '/home/wlodek/kea/src/bin/dhcp6'
  CXX      main.o
  CXX      dhcp6_log.lo
  CXX      dhcp6_srv.lo
  CXX      ctrl_dhcp6_srv.lo
  CXX      json_config_parser.lo
  CXX      dhcp6to4_ipc.lo
  CXX      client_handler.lo
  CXX      dhcp6_lexer.lo
  CXX      dhcp6_parser.lo
  CXX      parser_context.lo
  CXX      dhcp6_messages.lo
  CXXLD    libdhcp6.la
  CXXLD    kea-dhcp6
make[5]: Leaving directory '/home/wlodek/kea/src/bin/dhcp6'
Making all in tests
make[5]: Entering directory '/home/wlodek/kea/src/bin/dhcp6/tests'
Making all in .
make[6]: Entering directory '/home/wlodek/kea/src/bin/dhcp6/tests'
  CXX      libco1_la-callout_library_1.lo
  CXX      libco2_la-callout_library_2.lo
  CXX      libco3_la-callout_library_3.lo
  CXXLD    libco2.la
  CXXLD    libco1.la
  CXXLD    libco3.la
make[6]: Leaving directory '/home/wlodek/kea/src/bin/dhcp6/tests'
make[5]: Leaving directory '/home/wlodek/kea/src/bin/dhcp6/tests'

make[5]: Entering directory '/home/wlodek/kea/src/lib/util/unittests'
  CXX      libutil_unittests_la-fork.lo
  CXX      libutil_unittests_la-newhook.lo
  CXX      libutil_unittests_la-testdata.lo
  CXXLD    libutil_unittests.la
make[5]: Leaving directory '/home/wlodek/kea/src/lib/util/unittests'

and

make[6]: Entering directory '/home/wlodek/kea/src/lib/log/tests'
  CXX      logger_example-logger_example.o
  CXX      init_logger_test-init_logger_test.o
  CXX      buffer_logger_test-buffer_logger_test.o
  CXX      logger_lock_test-logger_lock_test.o
  CXX      logger_lock_test-log_test_messages.o
  CXXLD    init_logger_test
  CXXLD    buffer_logger_test
  CXXLD    logger_example
  CXXLD    logger_lock_test
make[6]: Leaving directory '/home/wlodek/kea/src/lib/log/tests'