Skip preview jobs on fork repositories (#763)

* Skip preview jobs on fork repositories

* Add explaining comment

Author: reakaleek

.github/workflows/preview-build.yml

@@ -45,6 +45,7 @@ permissions:
 
 jobs:
   build:
+    if: github.event.repository.fork == false # Skip running the job on the fork itself (It still runs on PRs on the upstream from forks)
     concurrency:
       group: ${{ github.workflow }}-${{ github.event.pull_request.head.ref || github.ref }}
       cancel-in-progress: ${{ startsWith(github.event_name, 'pull_request') }}

.github/workflows/preview-cleanup.yml

@@ -12,6 +12,7 @@ permissions:
 
 jobs:
   destroy:
+    if: github.event.repository.fork == false # Skip running the job on the fork itself (It still runs on PRs on the upstream from forks)
     runs-on: ubuntu-latest
     steps:
       - name: Delete GitHub environment
@@ -53,4 +54,4 @@ jobs:
           aws s3 rm "s3://elastic-docs-v3-website-preview/${GITHUB_REPOSITORY}/pull/${PR_NUMBER}" --recursive
 
       - name: 'Update Reference Index'
-        uses: elastic/docs-builder/actions/update-reference-index@main
+        uses: elastic/docs-builder/actions/update-reference-index@main