[Bug preprocessor/85211] -isystem automatically adds extern "C" to includes

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85211

--- Comment #6 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to blastrock from comment #5)
> So is this a regression since #37727 was fixed?

PR 37727 is not fixed, it's still NEW.