chore: update embedded zccache dependency

[zackees]

Advances fbuild's embedded zccache dependency from 3f9d4e6 to upstream 9bc8b4d, consistently across all platform/build crates. The lockfile now resolves zccache's current dependency set, including kernal-api 0.1.23.

This brings the embedded service onto the latest upstream implementation after the previous pin. The published ESP32-S3 cold benchmark will be rerun after merge to measure the effect.

Validation:

• soldr cargo check -p fbuild-build -p fbuild-build-engine -p fbuild-build-esp -p fbuild-build-mcu -p fbuild-build-arm --all-targets
• soldr cargo test -p fbuild-build --test zccache_embedded_smoke (2 passed, including cold miss followed by warm hit)
• git diff --check

The benchmark workflow's path filter does not include these dependency manifests, so it must be dispatched on main after this PR merges.

[coderabbitai]

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📥 Commits

Reviewing files that changed from the base of the PR and between 3d0682e and ea93d33.

⛔ Files ignored due to path filters (1)

• Cargo.lock is excluded by !**/*.lock

📒 Files selected for processing (5)

• crates/fbuild-build-arm/Cargo.toml
• crates/fbuild-build-engine/Cargo.toml
• crates/fbuild-build-esp/Cargo.toml
• crates/fbuild-build-mcu/Cargo.toml
• crates/fbuild-build/Cargo.toml

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