Compilation of rust-demangle.c fails on MinGW

[Eli Zaretskii]

> Date: Wed, 4 Aug 2021 15:41:30 +0100
> From: Jonathan Wakely <jwakely@redhat.com>
> Cc: gcc-bugs@gcc.gnu.org, eliz@gnu.org
> 
> > The libiberty README says to report bugs to gcc-bugs@gcc.gnu.org.
> 
> Well that needs to be fixed. It should point to
> https://gcc.gnu.org/bugs/ instead.

Which points to GCC Bugzilla, which doesn't have a "libiberty"
component.  So I suggest to add such a component on the Bugzilla.