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.
It's a pain having it in a rule in Makefile.gtk, which isn't even the
recommended makefile these days - it can't be re-run conveniently, and
there's no way to parametrise it. Now it can be run no matter which
makefile you're using, and it lets you narrow down to a subset of
games (though not presets). Other options could easily be added.
