[m-rev.] for review: start on replacing --intermod-directories and related options

[Zoltan Somogyi]

On 2024-11-15 17:36 +11:00 AEDT, "Zoltan Somogyi" <zoltan.somogyi at runbox.com> wrote:

> It turns out the diff broke the ability to bootstrap with --intermod-opt,
> which is strange, because even a bootstrap without --intermod-opt
> does intermodule optimization in the library directory. The symptom
> of the breakage is the same I worked around for the valid_seq and
> warnings test cases: an error message about not finding a .opt file,
> because we try to read it *without* building it. It seems that looking
> for .m files instead of .opt files was a workaround for the fact that
> --intermod-opt never worked *properly*, i.e. as intended, in the first place :-(

The above paragraph turned out to be wrong-headed.

> I am now testing whether the reason why intermod opt works
> in the library directory is that it also enables transitive optimization.
> Tomorrow I will look into what extra dependencies we need to add
> to .d files to prevent the issue, but the rotd tests tonight will fail
> due to this problem.

The fix is to (a) put back the code that the bad diff deleted, but
(b) *document* what it does, and why it does it, properly. I have now
done (a), and will do (b) as soon as I have nailed down some details.

Zoltan.