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

[i.nixman at autistici dot org]

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

--- Comment #2 from niXman <i.nixman at autistici dot org> ---
Created attachment 40966
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=40966&action=edit
patch