[Bug libstdc++/84159] filesystem::path::operator/= with has root directory path

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84159

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|---                         |FIXED

--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Fixed for 8.2, thanks for the report.