ci: stop caching the zig linker toolchain

[orangeCatDeveloper]

Summary

mlugg/setup-zig saves the global zig cache under a key that includes the run id, so every cli-package-validation run adds an entry that no later run restores. The repository cache is over its 10 GB quota, and those entries are crowding out the Rust build cache that keeps Build CLI release candidate at 45 s instead of 185 s. zig only links here, so the cache carries nothing worth keeping; turn it off.

Verification

Repository cache before this change:

$ gh api repos/apache/maka/actions/cache/usage
active_caches_size_in_bytes: 10710617722   active_caches_count: 81

setup-zig-cache-v2-...-0.16.0--35050097005-1   22 MB   refs/heads/main
setup-zig-cache-v2-...-0.16.0--35055705222-2   22 MB   refs/pull/5308/merge
... 43 entries, 1.00 GB, one per run

Cost on the linux jobs of run 35125665522: the save step (Post Install the Linux baseline linker) took 1–2 s per job, and Build the release addon takes 10–18 s with or without a warm zig cache. No wall-clock change expected; the change is cache hygiene.

AI use

Select exactly one:

• No generative tool made a substantive contribution
• Generative tooling made a substantive contribution

Tool(s) and scope: Claude Code audited the repository cache, traced the entries to setup-zig's run-scoped key, and wrote the change.

Checklist

• Tests cover the change and fail without it
• Lint, format, typecheck and the affected suites pass locally

Does this PR entail a change in behavior?

• Yes — described under Summary above
• No

[orangeCatDeveloper]

Opened by mistake while testing on a fork; closing. Will reopen once the change has been validated.