[Bug c/65377] [5.0 Regression] cpp attribute check ala clang fails to compile

[trippels at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65377

--- Comment #7 from Markus Trippelsdorf <trippels at gcc dot gnu.org> ---
Unfortunately https://gcc.gnu.org/ml/gcc-patches/2015-01/msg02357.html hasn't
been checked in yet.