[Bug driver/108865] gcc on Windows fails with Unicode path to source file

["costas.argyris at gmail dot com" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108865

--- Comment #33 from Costas Argyris <costas.argyris at gmail dot com> ---
It should be noted that with the current implementation, windres (part of
binutils) is mandatory when building for the mingw (Windows) hosts, both 32 and
64-bit versions.

That is, a build failure will occur if windres is not found for the mingw
hosts.

This means that for these hosts, gcc will *always* be built with UTF-8 as its
active code page on Windows, thereby eliminating the need to have a way to
query the active code page as a user.

If for example, it could be built either with or without windres, then the
active code page would also be conditional on that, so users would need a way
to tell what is the active code page being used by a given gcc.exe or g++.exe
executable.    By having windres be a mandatory build tool for the mingw hosts,
this is not a requirement because the answer will always be UTF-8 (otherwise
the build would have failed).

This is all relevant for gcc 13 or later (as per Target Milestone above) and a
minimum Windows Version 1903 (May 2019 Update).    If gcc is 13 or later but
Windows version is earlier than the minimum target version, gcc will not be
using UTF-8 as its active code page on its own - it will still be possible to
make it though by applying the UTF-8 manifest with mt.exe manually, or by
checking the Windows checkbox that sets UTF-8 globally.