The good old () vs (void) issue.
For reference this is now tracked upstream: https://sourceforge.net/p/elftoolchain/tickets/491/
(Actually 3 levels upstream: FreeBSD - libcxxrt - ELF tool chain)
Other issues encountered by *san tests have been addressed (e.g. extra 'E's in demangled output), but all will take some time to make it into a FreeBSD release.