[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 #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
This behaviour is target-dependent. If the target defines NO_IMPLICIT_EXTERN_C
then it doesn't happen.