[Bug bootstrap/67546] bootstrap broken on x86_64-w64-mingw32, error: '::unsetenv' has not been declared in gcc.c

[dmalcolm at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67546

--- Comment #5 from David Malcolm <dmalcolm at gcc dot gnu.org> ---
Is this a duplicate of PR 67363?