This port has no reverse dependencies according to FreshPorts and is unsupported upstream. Supported GCC versions are now 10, 11 and 12 and GCC 13 should be released soon. GCC_DEFAULT is now 12. The port should probably be deprecated and then removed.
Fixed by jhb@ with commit https://cgit.freebsd.org/ports/commit/?id=005a11536950f4031a3efbf86aa7c06c3fbfaef4 .