[Bug c++/109653] [[clang::fallthrough]] recognised up to g++ v12 not not g++ v13

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109653

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Hmm, __has_cpp_attribute never returns 0 for unknown attributes

#if defined __has_cpp_attribute 
#  if __has_cpp_attribute (fakeattribute)
#    error errorout
#  endif
#endif

I thought it should.