fix(ci): detect and set CARGO_HOME explicitly for rust tests

[Claude]

The dtolnay/rust-toolchain action installs Rust binaries to ~/.cargo/bin but doesn't set the CARGO_HOME environment variable. Without CARGO_HOME, the container entrypoint can't add Cargo binaries to PATH, causing rustc --version and cargo --version tests to fail with exit code 127.

Changes

• Detect CARGO_HOME from cargo binary location using which cargo | dirname | dirname
• Fall back to ~/.cargo if cargo not found
• Always set CARGO_HOME in $GITHUB_ENV regardless of whether it was pre-set

Before:

if [ -n "$CARGO_HOME" ]; then
  echo "CARGO_HOME=${CARGO_HOME}" >> $GITHUB_ENV
fi

After:

if [ -n "$CARGO_HOME" ]; then
  CARGO_HOME_VALUE="$CARGO_HOME"
else
  CARGO_BIN=$(which cargo 2>/dev/null || echo "")
  if [ -n "$CARGO_BIN" ]; then
    CARGO_HOME_VALUE=$(dirname "$(dirname "$CARGO_BIN")")
  else
    CARGO_HOME_VALUE="$HOME/.cargo"
  fi
fi
echo "CARGO_HOME=${CARGO_HOME_VALUE}" >> $GITHUB_ENV

This ensures the environment variable propagates through the chain: workflow → Node.js process (process.env.CARGO_HOME) → container env var (AWF_CARGO_HOME) → chroot PATH ($CARGO_HOME/bin).

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• https://api.github.com/graphql
  • Triggering command: /usr/bin/gh gh pr checks --json name,state,link --abbrev-ref HEAD /home/REDACTED/.local/bin/git (http block)
  • Triggering command: /usr/bin/gh gh pr view 745 --json isDraft,statusCheckRollup (http block)
• https://api.github.com/repos/github/gh-aw-firewall/actions/runs
  • Triggering command: /usr/bin/gh gh run list --branch claude/fix-github-actions-workflow-again --limit 5 --json workflowName,status,conclusion,createdAt,headSha /home/REDACTED/.nvm/package.json /home/REDACTED/.nvm/rename_test.sh /home/REDACTED/.nvm/test -n 1000 (http block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

[Copilot]

Pull request overview

This PR fixes CARGO_HOME detection in the GitHub Actions test-chroot workflow. The dtolnay/rust-toolchain action installs Rust to ~/.cargo/bin but doesn't set the CARGO_HOME environment variable, causing tests to fail when the container entrypoint tries to add Cargo binaries to PATH.

Changes:

• Detect CARGO_HOME from cargo binary location using which cargo | dirname | dirname
• Fall back to ~/.cargo if cargo is not found
• Always set CARGO_HOME in $GITHUB_ENV to ensure it propagates to the container
• Update comment to correctly state that rust-toolchain action doesn't set CARGO_HOME

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