[Bug libstdc++/98985] libstdc++: filesystem::rename not overwriting files on Windows

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98985

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
I'll fix it by using MoveFileExW in posix::rename instead.

MoveFileExW seems to have some weird differences from POSIX rename when the
source or destination name is a directory.