sagemathgh-36829: CI Linux incremental: `make reconfigure` after uninstalling packages
    
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As observed in
sagemath#36792 (comment), the
"CI Linux incremental" workflow, which is run when package scripts are
updated, is not helpful when testing new or modified `spkg-configure.m4`
scripts when the SPKG has been installed:

Although we uninstall packages with changed spkg-configure.m4 scripts
already, a re-run of configure is not (always?) triggered.

So here we invoke it explicitly, using a new makefile target `make
reconfigure`.
(This new target also simplifies instructions issued by the system
package advice facility.)

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URL: sagemath#36829
Reported by: Matthias Köppe
Reviewer(s): Kwankyu Lee, Matthias Köppe

sagemathgh-36997: `build/pkgs/{givaro,fflas_ffpack,linbox}`: Accept matching set of new versions
    
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Resolves sagemath#34359.

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### ⌛ Dependencies

- Depends on sagemath#36829 (to help with testing)

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URL: sagemath#36997
Reported by: Matthias Köppe
Reviewer(s):