[Bug libstdc++/83306] filesystem_error is not nothrow copyable

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83306

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
           Assignee|unassigned at gcc dot gnu.org      |redi at gcc dot gnu.org
   Target Milestone|---                         |9.0

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
I think I should also avoid storing the extra std::string and just do the
concatenation before passing the string to the system_error base class.