A Linux build job has many steps. One step calculates BUILD_DIR and wants later steps in that same job to receive it as an environment variable. Which command pattern is appropriate?

1. Append BUILD_DIR=the-value to the file identified by GITHUB_ENV.
2. Write BUILD_DIR into the runner temporary directory with no subsequent read step.
3. Append BUILD_DIR to GITHUB_STEP_SUMMARY.
4. Export BUILD_DIR in a shell process and rely on that export for all subsequent steps.