[Bug driver/71850] @file should be used to cc1/cc1plus when @file is used

["andrewjcg at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71850

Andrew Gallagher <andrewjcg at gmail dot com> changed:

           What    |Removed                     |Added
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                 CC|                            |andrewjcg at gmail dot com

--- Comment #5 from Andrew Gallagher <andrewjcg at gmail dot com> ---
I'm interesting in attempting to fix this, but first wanted some guidance on
where to look.  After an initial skim, what about modifying the `execute`
function to always serialize `command[n].argv` to an @file when executing the
command if `at_file_supplied`?  The main downside I see here is that it assumes
all subcommands support @file syntax when the frontend does.