[Bug libstdc++/79820] std::ifstream sets errno to zero

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79820

--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Sorry, I was looking at gcc-6-branch which sets errno=0 in close(), but I
removed that on trunk for PR 65411.