[Bug libstdc++/70360] --enable-vtable-verify

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70360

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
... and the testsuite doesn't know how to test the ABI for every configuration
that alters the ABI.