This adds sizes 24×24 (common on Linux desktop, for instance in
application bars), as well as 64×64 and 128×128 (common on Linux
mobile).

I kept the existing border sizes, but using the same one from 44×44 to
96×96 sounds a bit weird, it’d probably be best to revisit them at some
point.

Signed-off-by: Emmanuel Gil Peyrot <linkmauve@linkmauve.fr>

Preferences that adjust the display, such as Pearl graphics style or
Light Up lit-blobs toggling, shouldn't affect the official icons, even
if a ~/.config/sgt-puzzles exists in the account that builds the
puzzles.

If you configure a Linux build of Puzzles with -fsanitize=address, it
will fail during the icons build, because the icon-maker programs leak
memory when they're run, and by default, this causes ASan to report
all the memory leaks at the end of the program *and then exit 1*.

I don't think 'just fix the memory leaks' is a viable answer. _Some_
of the leaks come from the Puzzles code, and could be fixed by being
more punctilious about freeing everything before exiting (although
that is not necessary for any actually sensible purpose and would
_only_ serve to stop Leak Sanitiser complaining). But some are outside
the Puzzles code completely, apparently from fontconfig. So even if we
fixed all the leaks we could find, we wouldn't prevent the failure
status.

When I want to build with ASan, I've been working around this by
setting ASAN_OPTIONS=detect_leaks=0 in the environment before running
the build command. Easier all round if we just do that _inside_ the
cmake setup.

It wants a 240x130 pixel JPEG.  I've gone for rotating the screenshot
a bit because the store overlays text on the picture and I don't want
horizontal lines in the picture confusing the text.  I think the store
handles dimming the image, so the picture we produce is at full
brightness.

These are built alongside other icons as part of the GTK build.  It
builds new icon sizes of 44 and 88 pixels and then uses ImageMagick to
round off the corners and add a shadow in accordance with the KaiOS
design guide.

They've been broken since the move to CMake, which had an incorrect
variable substitution in the --redo argument.

This is similar in concept to Minesweeper, in that each clue tells you
the number of things (in this case, just 'black squares') in the
surrounding 3x3 grid section.

But unlike Minesweeper, there's no separation between squares that can
contain clues, and squares that can contain the things you're looking
for - a clue square may or may not itself be coloured black, and if
so, its clue counts itself.

So there's also no hidden information: the clues can all be shown up
front, and the difficulty arises from the game generator choosing
which squares to provide clues for at all.

Contributed by a new author, Didi Kohen. Currently only has one
difficulty level, but harder ones would be possible to add later.

This allows the icons build to automatically disable itself if Perl
can't be found at all (and print a warning explaining that that's
why). It also means that if Perl exists on the system but is somewhere
other than /usr/bin (where our #! lines expect it), the icons build
can still run.