* Update to 4.4.2
4.4.0 increased the ZScript version number, GZDoom 4.4.1 and 4.4.2 have some bugfixes.
* Fix bad checksum
Old hash was done without `--unpack` option, resulting in a mismatch.
* Fetch submodules
This fixes the issue with `zmusic` not being brought in as a dependency.
* Add zmusic derivation
Since zmusic isn't actually a submodule, we have to derive it ourselves and pass it as a buildInput.
* Semicolon.
* Semicolon in the *right* place this time.
* Merge the zmusic source into the gzdoom source.
Apparently this is how they expect zmusic to be added. Why this isn't a submodule, I don't know.
* Fix bad path editing
Credit to Open Skies for fixing this. Turns out the paths edited in the `gzdoom` derivation were for zmusic, which needs these edits to be made so that it looks in nix-friendly places for its stuff.