There's no reason to put the .rc file into developer tools like
galaxieseditor at all. Its current job is to add an icon, and those
tools don't have any. I'm about to add version information, and they
won't have that either (in particular, no description string like the
games do).

The CLI developer tools already don't include puzzles.rc, and GUI dev
tools are more like those than they are like puzzles.

puzzles.rc was being added to an aux GUI tool's source file list by
get_platform_puzzle_extra_source_files(), which is called for aux GUI
tools as well as for puzzles proper. However, it's not as simple as
just eliminating that call, because on Unix, we _do_ need to add the
same extra source files to GUI dev tools that we do for puzzles,
because gtk.c contains external references to either an array of the
puzzle's icons or an empty array indicating that there aren't any, so
_something_ has to provide that.

So instead, get_platform_puzzle_extra_source_files now takes an extra
argument saying whether the program is a real puzzle or an aux tool;
windows.cmake leaves out puzzles.rc in the latter case, but unix.cmake
puts the icon array in unconditionally.

The 'core' library contains almost all the same objects as 'common',
but leaves out hat.c. And the auxiliary program 'hatgen' now links
against that slightly reduced core library instead of 'common'.

This avoids a dependency loop: one of hatgen's jobs is to generate
hat-tables.h, but hat-tables.h is a dependency of it.

Of course, the generated hat-tables.h is already committed, so this
doesn't present a bootstrapping problem in a normal build. But if
someone modifies hatgen.c in order to regenerate hat-tables.h, and
does so in a way that makes it uncompilable, they can't rebuild hatgen
and try again! Of course you can always revert changes with git, but
it's annoying to have to. Better to keep the dependencies non-cyclic
in the first place.

This fixes a build failure introduced by commit 2e48ce132e011e8
yesterday.

When I saw that commit I expected the most likely problem would be in
the NestedVM build, which is currently the thing with the most most
out-of-date C implementation. And indeed the NestedVM toolchain
doesn't have <tgmath.h> - but much more surprisingly, our _Windows_
builds failed too, with a compile error inside <tgmath.h> itself!

I haven't looked closely into the problem yet. Our Windows builds are
done with clang, which comes with its own <tgmath.h> superseding the
standard Windows one. So you'd _hope_ that clang could make sense of
its own header! But perhaps the problem is that this is an unusual
compile mode and hasn't been tested.

My fix is to simply add a cmake check for <tgmath.h> - which doesn't
just check the file's existence, it actually tries compiling a file
that #includes it, so it will detect 'file exists but is mysteriously
broken' just as easily as 'not there at all'. So this makes the builds
start working again, precisely on Ben's theory of opportunistically
using <tgmath.h> where possible and falling back to <math.h>
otherwise.

It looks ugly, though! I'm half tempted to make a new header file
whose job is to include a standard set of system headers, just so that
that nasty #ifdef doesn't have to sit at the top of almost all the
source files. But for the moment this at least gets the build working
again.

After commit 1470c9530b1cff3 enabled assertions, I found that my build
scripts were complaining that the Windows binaries built from the same
source twice were not generating the same output, and it turned out to
be because the use of __FILE__ in every assert was baking in a
pathname from my build setup containing a mkstemp()-randomised path
component.

I've found the '-fmacro-prefix-map' option, available in both gcc and
clang (except the archaic gcc used by my NestedVM build, alas), which
lets you remap pathnames for purpose of what __FILE__ expands to. So
now our assertion statements should look as if the puzzle source just
lived in /puzzles, and (just in case a pathname in a generated header
ever becomes relevant) the cmake build directory is /build.

Despite the name, COMPILE_DEFINITIONS was only ever used to set a
single definition, and as far as I can tell that's all it could do
even when I tried to put them in a single word separated by
semicolons.  Turning COMPILE_DEFINITIONS into a multi-valued argument
seems to make it work much better.

Assertion failures are ugly, but they're better than the alternative.
Defensive coding is a general principle throughout Puzzles and I don't
think it's sensible to selectively turn that off.

The mechanism by which we re-enable assertions is stolen from PuTTY
(with an enhancement to cover MinSizeRel builds as well) and is pretty
ugly because CMake doesn't seem to have a good way to do it.

If I re-run cmake in a Unix build directory, it unconditionally
rewrites generated-games.h, which causes fuzzpuzz to be rebuilt. This
is a waste of effort in the extremely common case where the rewritten
generated-games.h is identical to the old one.

Now we write the data to a temporary file first, and use cmake's
'configure_file' command to copy that to generated-games.h, because it
so happens that configure_file checks if the two files are identical
and avoids updating the timestamp on the destination file if so.

(This will presumably also be a beneficial change on any other
platform that uses generated_games.h in the build, such as OS X. I
just hadn't noticed until it hit the build I most often re-run in an
existing build directory.)

cmake 3.21 has a more intuitively spelled command I could have used,
called 'file(COPY_FILE src dst ONLY_IF_DIFFERENT)'. But we currently
permit cmake all the way back to 3.5, so I can't use that.

All the not-quite-puzzle GUI programs (only galaxieseditor at this
point) were using the extra source files from Null Game, presumably as a
convenient way of asking not to have an icon on platforms where icons
are provided as extra source files.  Unfortunately, this all went wrong
if Null Game did have a save file for an icon, causing CMake to complain
about multiple definitions of a target.

Now these programs look for extra files under their own names, which
will work just as well since those have no save files to generate icons
from either.

I don't expect this to actually come up in any circumstance, but it
prevents a warning in some versions of gcc that would otherwise arise
from the use of 'int' to compute the input size: if gcc isn't
confident that the int is positive, then it complains that possible
inputs to malloc might be in the region of 2^64 - (small multiple of a
negative 32-bit int).

I would hope malloc would fail in any case on such an input, so
failing a couple of lines earlier makes no important difference.

Annoyingly, stdint.h is missing in my NestedVM build setup (though it
has stdbool.h - it's not _totally_ C90). So I have to check that at
cmake time.

Also, removed the #defines for smalloc and friends from the tree234
test mode. These were needed in the old build system, when
tree234-test was built ad-hoc without being linked against malloc.c.
But now tree234-test links against the same utils library as
everything else, and can use the real smalloc - and doing so prevents
another of these warnings when compiling with -flto.

It relied on reading gamedesc.txt to find a list of puzzle binaries to
run. But gamedesc.txt is now specific to the Windows build (since it
contains Windows executable names), and isn't available in the Unix
cmake build directory.

Fixed by making a simpler gamelist.txt available on all platforms.