gh-36731: `build/pkgs/pillow`: Allow discovery of libjpeg, upgrade to 10.1.0
<!-- ^^^^^
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 discussed in https://groups.google.com/g/sage-devel/c/A4nY3bh1oPI
@egourgoulhon
Here we make`libjpeg` a new "recommended" dummy package with spkg-
configure script -- same category as pandoc, ffmpeg, imagemagick,
texlive, so it appears in the installation instructions in
https://deploy-preview-36731--sagemath-
tobias.netlify.app/html/en/installation/source#debian-ubuntu-package-
installation (in the 3rd command line for each of the shown package
systems).
Use of libjpeg can be disabled using `./configure --without-system-
libjpeg`.
Everything done here would also be necessary if we decided to make
libjpeg a normal standard/optional package; that is beyond the scope of
this PR.
We also refine the "CI Linux incremental" workflow, which determines
what packages to uninstall (so that spkg-configure is tested) or to
build (important for optional packages), based on changed files.
Failures seen in https://github.com/sagemath/sage/actions/runs/691489095
0/job/18813211070?pr=36731#step:4:8 came from the workflow trying to
build dummy packages. We suppress these now, as seen in https://github.c
om/sagemath/sage/actions/runs/6915792754/job/18815135590?pr=36731#step:4
:8
Tests at https://github.com/mkoeppe/sage/actions/runs/6911535503
(Linux), https://github.com/mkoeppe/sage/actions/runs/6911535500 (macOS)
<!-- 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/36731
Reported by: Matthias Köppe
Reviewer(s): Eric Gourgoulhon
