`Install failed: EOF when reading a line` in blank GitHub Action

[thejcannon]

See https://github.com/pantsbuild/pantsbuild.org/actions/runs/7343898030/job/19995046003

Run PANTS_BOOTSTRAP_CACHE_KEY=$(PANTS_BOOTSTRAP_TOOLS=2 pants bootstrap-cache-key)
  PANTS_BOOTSTRAP_CACHE_KEY=$(PANTS_BOOTSTRAP_TOOLS=2 pants bootstrap-cache-key)
  if [[ "$OSTYPE" == "darwin"* ]]; then
    PANTS_BOOTSTRAP_CACHE_DIR="$HOME/Library/Caches/nce"
  else
    PANTS_BOOTSTRAP_CACHE_DIR="$HOME/.cache/nce"
  fi
  echo "pants_bootstrap_cache_key=$PANTS_BOOTSTRAP_CACHE_KEY" >> $GITHUB_OUTPUT
  echo "pants_bootstrap_cache_dir=$PANTS_BOOTSTRAP_CACHE_DIR" >> $GITHUB_OUTPUT
  shell: /usr/bin/bash --noprofile --norc -e -o pipefail {0}
No Pants configuration was found at or above /home/runner/work/pantsbuild.org/pantsbuild.org.
Install failed: EOF when reading a line
...

I suspect $(PANTS_BOOTSTRAP_TOOLS=2 pants bootstrap-cache-key) doesn't like a missing pants.toml and not being interactive.