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fix(derive): Track Cargo env vars for incremental rebuilds

fix(derive): Track Cargo env vars for incremental rebuilds: a task in repo2rlenv-pr-diff (Harbor dataset). Title: fix(derive): Track Cargo env vars for incremental rebuilds

The task

**Title:** fix(derive): Track Cargo env vars for incremental rebuilds

Part of FineEnvs/repo2rlenv-pr-diff.