This requires shuffling a bunch of stuff around to get a CLI lua
executable that uses an automation-like environment, but that's
something that'll be nice to have in the future anyway.
Busted indirectly depends on lfs and we currently can't use external
binary modules, so add a copy of lfs to the repo and build it with
Aegisub.
Aegisub needs Lua built as C++ (for stack unwinding on errors). No one
packages it like that, so at the moment we can't actually use systme
packages for Lua.
Fixes a bunch of memory leaks on Automation errors.
