Support non-ephemeral runners

[toast-gear]

If docker changes a file / folder on a mounted volume the permissions at borked, probably to root root. On a subsequent run the actions/checkout will fail as it can't clean the repo. You will get errors on any file this action touches, I think for this action the implications are just on the .terraform/ folder?

Example of the errors:

Command failed: rm -rf "/actions-runner/_work/repo/repo/.terraform"
rm: cannot remove '/actions-runner/_work/repo/repo/.terraform/modules/my_module/wrappers/main.tf': Permission denied

Here is an example of a fix another author did once I raised the issue with them:

dflook/terraform-github-actions@v1.17.0...v1.17.1

You can work around this by:

      - name: Get Actions user id
        id: get_uid
        run: |
          actions_user_id=`id -u $USER`
          echo $actions_user_id
          echo ::set-output name=uid::$actions_user_id
      - name: Correct Ownership in GITHUB_WORKSPACE directory
        uses: peter-murray/reset-workspace-ownership-action@v1
        with:
          user_id: ${{ steps.get_uid.outputs.uid }}
      - uses: actions/checkout@v2

but this is a faff and should be handled by the action natively