Build failure on macOS 15: Undefined symbols for architecture arm64

Full log below.

:info:build cd /opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_net_openvpn3/openvpn3/work/build/test/unittests && /opt/local/bin/cmake -E cmake_link_script CMakeFiles/coreUnitTests.dir/link.txt --verbose=ON
:info:build /usr/bin/clang++ -pipe -I/opt/local/libexec/openssl3/include -Os -DNDEBUG -I/opt/local/libexec/openssl3/include -isystem/opt/local/include -stdlib=libc++ -isysroot/Library/Developer/CommandLineTools/SDKs/MacOSX15.sdk -arch arm64 -isysroot /Library/Developer/CommandLineTools/SDKs/MacOSX15.sdk -mmacosx-version-min=15.0 -Wl,-search_paths_first -Wl,-headerpad_max_install_names -L/opt/local/libexec/openssl3/lib -L/opt/local/lib -Wl,-headerpad_max_install_names -Wl,-ld_classic -Wl,-syslibroot,/Library/Developer/CommandLineTools/SDKs/MacOSX15.sdk CMakeFiles/coreUnitTests.dir/core_tests.cpp.o CMakeFiles/coreUnitTests.dir/test_acc.cpp.o CMakeFiles/coreUnitTests.dir/test_acc_certcheck.cpp.o CMakeFiles/coreUnitTests.dir/test_route_emulation.cpp.o CMakeFiles/coreUnitTests.dir/test_log.cpp.o CMakeFiles/coreUnitTests.dir/test_comp.cpp.o CMakeFiles/coreUnitTests.dir/test_b64.cpp.o CMakeFiles/coreUnitTests.dir/test_verify_x509_name.cpp.o CMakeFiles/coreUnitTests.dir/test_ssl.cpp.o CMakeFiles/coreUnitTests.dir/test_sslctx.cpp.o CMakeFiles/coreUnitTests.dir/test_continuation.cpp.o CMakeFiles/coreUnitTests.dir/test_crypto.cpp.o CMakeFiles/coreUnitTests.dir/test_optfilt.cpp.o CMakeFiles/coreUnitTests.dir/test_clamp_typerange.cpp.o CMakeFiles/coreUnitTests.dir/test_pktstream.cpp.o CMakeFiles/coreUnitTests.dir/test_remotelist.cpp.o CMakeFiles/coreUnitTests.dir/test_relack.cpp.o CMakeFiles/coreUnitTests.dir/test_http_proxy.cpp.o CMakeFiles/coreUnitTests.dir/test_peer_fingerprint.cpp.o CMakeFiles/coreUnitTests.dir/test_safestr.cpp.o CMakeFiles/coreUnitTests.dir/test_numeric_cast.cpp.o CMakeFiles/coreUnitTests.dir/test_dns.cpp.o CMakeFiles/coreUnitTests.dir/test_header_deps.cpp.o CMakeFiles/coreUnitTests.dir/test_capture.cpp.o CMakeFiles/coreUnitTests.dir/test_cleanup.cpp.o CMakeFiles/coreUnitTests.dir/test_crypto_hashstr.cpp.o CMakeFiles/coreUnitTests.dir/test_csum.cpp.o CMakeFiles/coreUnitTests.dir/test_format.cpp.o CMakeFiles/coreUnitTests.dir/test_headredact.cpp.o CMakeFiles/coreUnitTests.dir/test_hostport.cpp.o CMakeFiles/coreUnitTests.dir/test_ip.cpp.o CMakeFiles/coreUnitTests.dir/test_ostream_containers.cpp.o CMakeFiles/coreUnitTests.dir/test_parseargv.cpp.o CMakeFiles/coreUnitTests.dir/test_path.cpp.o CMakeFiles/coreUnitTests.dir/test_pktid.cpp.o CMakeFiles/coreUnitTests.dir/test_prefixlen.cpp.o CMakeFiles/coreUnitTests.dir/test_randapi.cpp.o CMakeFiles/coreUnitTests.dir/test_rc.cpp.o CMakeFiles/coreUnitTests.dir/test_route.cpp.o CMakeFiles/coreUnitTests.dir/test_reliable.cpp.o CMakeFiles/coreUnitTests.dir/test_splitlines.cpp.o CMakeFiles/coreUnitTests.dir/test_statickey.cpp.o CMakeFiles/coreUnitTests.dir/test_streq.cpp.o CMakeFiles/coreUnitTests.dir/test_time.cpp.o CMakeFiles/coreUnitTests.dir/test_typeindex.cpp.o CMakeFiles/coreUnitTests.dir/test_tun_builder.cpp.o CMakeFiles/coreUnitTests.dir/test_userpass.cpp.o CMakeFiles/coreUnitTests.dir/test_validatecreds.cpp.o CMakeFiles/coreUnitTests.dir/test_weak.cpp.o CMakeFiles/coreUnitTests.dir/test_cliopt.cpp.o CMakeFiles/coreUnitTests.dir/test_buffer.cpp.o CMakeFiles/coreUnitTests.dir/test_proto.cpp.o CMakeFiles/coreUnitTests.dir/test_openssl_x509certinfo.cpp.o CMakeFiles/coreUnitTests.dir/test_openssl_authcert.cpp.o CMakeFiles/coreUnitTests.dir/test_opensslpki.cpp.o CMakeFiles/coreUnitTests.dir/test_openssl_misc.cpp.o CMakeFiles/coreUnitTests.dir/test_session_id.cpp.o CMakeFiles/coreUnitTests.dir/test_buffer_ip.cpp.o CMakeFiles/coreUnitTests.dir/test_cpu_time.cpp.o CMakeFiles/coreUnitTests.dir/test_misc_unix.cpp.o CMakeFiles/coreUnitTests.dir/test_pipe.cpp.o CMakeFiles/coreUnitTests.dir/test_psid_cookie.cpp.o -o coreUnitTests  -Wl,-rpath,/opt/local/lib /opt/local/lib/liblz4.dylib /opt/local/libexec/openssl3/lib/libssl.dylib -framework CoreFoundation -framework IOKit -framework CoreServices -framework SystemConfiguration -lpthread /opt/local/lib/liblzo2.dylib ../../lib/libgtest_main.a ../../lib/libgmock.a /opt/local/libexec/openssl3/lib/libcrypto.dylib /opt/local/lib/libjsoncpp.a ../../lib/libgtest.a
:info:build ld: warning: -ld_classic is deprecated and will be removed in a future release
:info:build Undefined symbols for architecture arm64:
:info:build   "testing::internal::MakeAndRegisterTestInfo(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>>, char const*, char const*, char const*, testing::internal::CodeLocation, void const*, void (*)(), void (*)(), testing::internal::TestFactoryBase*)", referenced from:
:info:build       __GLOBAL__sub_I_test_acc.cpp in test_acc.cpp.o
:info:build       __GLOBAL__sub_I_test_acc_certcheck.cpp in test_acc_certcheck.cpp.o
:info:build       __GLOBAL__sub_I_test_route_emulation.cpp in test_route_emulation.cpp.o
:info:build       __GLOBAL__sub_I_test_log.cpp in test_log.cpp.o
:info:build       __GLOBAL__sub_I_test_comp.cpp in test_comp.cpp.o
:info:build       __GLOBAL__sub_I_test_b64.cpp in test_b64.cpp.o
:info:build       __GLOBAL__sub_I_test_verify_x509_name.cpp in test_verify_x509_name.cpp.o
:info:build       ...
:info:build   "testing::internal::ReportInvalidTestSuiteType(char const*, testing::internal::CodeLocation const&)", referenced from:
:info:build       testing::internal::ParameterizedTestSuiteInfo<InvalidConfigs>* testing::internal::ParameterizedTestSuiteRegistry::GetTestSuitePatternHolder<InvalidConfigs>(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>>, testing::internal::CodeLocation) in test_cliopt.cpp.o
:info:build       testing::internal::ParameterizedTestSuiteInfo<ValidConfigs>* testing::internal::ParameterizedTestSuiteRegistry::GetTestSuitePatternHolder<ValidConfigs>(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>>, testing::internal::CodeLocation) in test_cliopt.cpp.o
:info:build ld: symbol(s) not found for architecture arm64
:info:build clang++: error: linker command failed with exit code 1 (use -v to see invocation)
:info:build make[2]: *** [test/unittests/coreUnitTests] Error 1
:info:build make[2]: Leaving directory `/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_net_openvpn3/openvpn3/work/build'
:info:build make[1]: *** [test/unittests/CMakeFiles/coreUnitTests.dir/all] Error 2
:info:build make[1]: Leaving directory `/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_net_openvpn3/openvpn3/work/build'
:info:build make: *** [all] Error 2

main.log

Start with the macOS 15 arm64 link command for test/unittests/coreUnitTests and the attached main.log. Inspect the CMake configuration and GoogleTest libraries involved in that target, then reproduce the failure on the reported environment. Done means the coreUnitTests target links successfully and the unit-test build completes.