ASF Infrastructure Team has flagged a GitHub Actions workflow policy violation, inside our PR Labeling. We must remove pull_request_target before 6 Apr 2026, or ASF Infra will turn off all GitHub Builds: https://github.com/apache/nuttx/issues/18359
This PR reimplements the PR Labeling with two triggers: pull_request and workflow_run. We no longer need pull_request_target, which is an unsafe trigger and may introduce security vulnerabilities.
GitHub Actions `codelytv/pr-size-labeler` and `actions/labeler` don't work with the pull_request trigger, so we replaced them with our own code. The implementation is explained here: https://github.com/apache/nuttx/issues/18359
### Modified Files
`.github/workflows/labeler.yml`: Changed the (read-write) pull_request_target trigger to (read-only) pull_request trigger. Compute the Size Label (e.g. Size: XS) and Arch Labels (e.g. Arch: arm). Save the PR Labels into a PR Artifact.
`.github/labeler.yml`: Added comment to clarify that NuttX PR Labeler only supports a subset of the `actions/labeler` syntax: `changed-files` and `any-glob-to-any-file`
### New Files
`.github/workflows/pr_labeler.yml`: Contains the workflow_run trigger, which is executed upon completion of the pull_request trigger. Download the PR Labels from the PR Artifact. Write the PR Labels into the PR.
Signed-off-by: Lup Yuen Lee <luppy@appkaki.com>
