[m-rev.] for review: check_libgrades

[Julien Fischer]

On Sun, 21 Apr 2024, Zoltan Somogyi wrote:

> Fix some issues related to checking libraries.
> 
> compiler/check_libgrades.m:
>     Check whether the needed libraries exist for a given set of values for
>     the relevant options just once, by recording the result the first time,
>     and reusing those results if the option values have not changed.
> 
> compiler/mercury_compile_main.m:
>     Delete an old and obsolete large comment about checking libraries.
>
>     Do not attempt to generate executables if some library is missing.
>     To make the code more readable, move the code for generating executables
>     to a separate predicate.
>
>     Do not mix any error_specs for missing libraries with module-specific
>     error_specs, since they are NOT module-specific.

That's fine.

Julien.