Use pull_request_target

Author: colluca

.github/workflows/gitlab-ci.yaml

@@ -6,17 +6,19 @@
 name: gitlab-ci
 # Skip on pull requests as forks don't have required secrets,
 # and pull requests from own repo already trigger a push event.
-on: [push, workflow_dispatch]
+on: [push, pull_request]
 jobs:
   gitlab-ci:
     name: Internal Gitlab CI
     runs-on: ubuntu-22.04
     steps:
       - name: Check Gitlab CI
-        uses: pulp-platform/pulp-actions/gitlab-ci@v2.1.0
+        uses: pulp-platform/pulp-actions/gitlab-ci@v2.4.1
         # Skip on forks due to missing secrets.
         if: >
-          github.repository == 'pulp-platform/snitch_cluster'
+          github.repository == 'pulp-platform/snitch_cluster' &&
+          (github.event_name != 'pull_request' ||
+          github.event.pull_request.head.repo.full_name != github.repository)
         with:
           domain: iis-git.ee.ethz.ch
           repo: github-mirror/snitch_cluster