Zig releases the toolchain at a specific commit at https://ziglang.org/builds/zig-xxx.

We currently support specifying the toolchain with released versions or master, but it can be an advanced requirement to hardcode the download URL.

We can factor out the steps to resolve the URL and support passing user-define URLs via input.

I don't have time to work on it now and it seems no real-world user requirement for it. Thus I tend to leave it as help wanted good first issue until a real-world use case is reported or someone takes it up.