gh-36829: CI Linux incremental: `make reconfigure` after uninstalling packages
<!-- ^^^^^
Please provide a concise, informative and self-explanatory title.
Don't put issue numbers in there, do this in the PR body below.
For example, instead of "Fixes #1234" use "Introduce new method to
calculate 1+1"
-->
<!-- Describe your changes here in detail -->
As observed in
https://github.com/sagemath/sage/pull/36792#issuecomment-1841713301, 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.)
<!-- Why is this change required? What problem does it solve? -->
<!-- If this PR resolves an open issue, please link to it here. For
example "Fixes #12345". -->
<!-- If your change requires a documentation PR, please link it
appropriately. -->
### :memo: Checklist
<!-- Put an `x` in all the boxes that apply. -->
<!-- If your change requires a documentation PR, please link it
appropriately -->
<!-- If you're unsure about any of these, don't hesitate to ask. We're
here to help! -->
<!-- Feel free to remove irrelevant items. -->
- [x] The title is concise, informative, and self-explanatory.
- [x] The description explains in detail what this PR is about.
- [x] I have linked a relevant issue or discussion.
- [ ] I have created tests covering the changes.
- [ ] I have updated the documentation accordingly.
### :hourglass: Dependencies
<!-- List all open PRs that this PR logically depends on
- #12345: short description why this is a dependency
- #34567: ...
-->
<!-- If you're unsure about any of these, don't hesitate to ask. We're
here to help! -->
URL: https://github.com/sagemath/sage/pull/36829
Reported by: Matthias Köppe
Reviewer(s): Kwankyu Lee, Matthias Köppe
