Bundle new build toolchain for gcc-mips-linux-gnu

It would seem that all mips gcc packages are no longer available through apt as of Ubuntu 25.10, which is...a problem to put simply.

We should explore toolchain alternatives for WSL/Ubuntu users, and flesh out docker/podman containerization instructions if they aren't sufficient already.

Not marked as "blocker" since the toolchain itself may not need to be directly bundled with HackerSM64 (we could maybe put together something that works universally across HackerN64). And any documentation changes would be made to the Wiki, which isn't tied to the source code.