Update Zig and use the x86_64 backend and incremental compilation

[IntegratedQuantum]

• [x] Enable the x86_64 backend in debug mode (done in Zig master)
• [ ] Fix graphics issues with x86_64 enabled (→caused by https://github.com/ziglang/zig/issues/24179)
• [x] Fix crash when opening the debug window with x86_64 enabled
• [ ] Upload a new zig version to our mirror
• [ ] Check if incremental compilation works and enable it

[IntegratedQuantum]

~~Currently blocked by https://github.com/ziglang/zig/issues/24179~~

[IntegratedQuantum]

Currently blocked by https://github.com/ziglang/zig/issues/24144, particularly waiting on better array access (which I believe is tracked by https://github.com/ziglang/zig/issues/24183).

[Daggerfall-is-the-best-TES-game]

Was this blocker https://github.com/ziglang/zig/issues/24144 fixed by https://github.com/ziglang/zig/pull/25154 ?

[IntegratedQuantum]

yes, but there is another blocker. I continued this in #2009