[Reland] Skip building Apple demo app on fork PRs

Author: huydhn

.github/workflows/apple.yml

@@ -42,6 +42,8 @@ jobs:
 
   build-demo-ios:
     name: build-demo-ios
+    # NB: Don't run this on fork PRs because they won't have access to the secret and would fail anyway
+    if: ${{ !github.event.pull_request.head.repo.fork }}
     uses: pytorch/test-infra/.github/workflows/macos_job.yml@main
     secrets: inherit
     with:
@@ -190,6 +192,8 @@ jobs:
         ) done
 
   upload-frameworks-ios:
+    # NB: Don't run this on fork PRs because they won't have access to the secret and would fail anyway
+    if: ${{ !github.event.pull_request.head.repo.fork }}
     runs-on: ubuntu-22.04
     needs: [build-frameworks-ios, set-version]
     timeout-minutes: 30
@@ -278,6 +282,8 @@ jobs:
 
   build-benchmark-app:
     name: build-benchmark-app
+    # NB: Don't run this on fork PRs because they won't have access to the secret and would fail anyway
+    if: ${{ !github.event.pull_request.head.repo.fork }}
     uses: pytorch/test-infra/.github/workflows/macos_job.yml@main
     secrets: inherit
     with: