[m-rev.] for review: fix a heisenbug in grade_lib

[Julien Fischer]

On Sun, 21 Apr 2024, Zoltan Somogyi wrote:

> On 2024-04-21 13:49 +10:00 AEST, "Julien Fischer" <jfischer at opturion.com> wrote:
>>>     - the names of the filed containing these modules, grade_solver.m,
>>
>> s/filed/files/
>
> Done. Thanks for the review.
>
> When I first brought up this Heisenbug a few months ago, you said
> you did not get it. Is that because you usually do an explicit mmake depend
> without -jN between configure and a full mmake?

Yes, when I build Mercury I usually do the depend step separately.
The place I have observed this bug occurring is in the 'tar' target that
is used when building the ROTDS.

Julien.