Exclude pushing packages to PR feed if from a fork (won't have secret)

Author: michael-hawker

.github/workflows/build.yml

@@ -158,8 +158,8 @@ jobs:
         run: ./PackEachExperiment.ps1 -date ${{ env.VERSION_DATE }} -postfix ${{ env.VERSION_PROPERTY }}
 
       # Push Pull Request Packages to our DevOps Artifacts Feed (see nuget.config)
-      - name: Push Pull Request Packages
-        if: ${{ env.IS_PR == 'true' }}
+      - name: Push Pull Request Packages (if not fork)
+        if: ${{ env.IS_PR == 'true' && github.event.pull_request.head.repo.full_name == github.repository && github.actor != 'dependabot[bot]' }}
         run: |
           dotnet nuget add source https://pkgs.dev.azure.com/dotnet/CommunityToolkit/_packaging/CommunityToolkit-PullRequests/nuget/v3/index.json `
             --name PullRequests `
@@ -232,10 +232,10 @@ jobs:
           path: |
             ${{ github.workspace }}/.github/workflows/SignClientFileList.txt
 
-      # if we're not doing a PR build then we upload our packages so we can sign as a separate job.
+      # if we're not doing a PR build (or it's a PR from a fork) then we upload our packages so we can sign as a separate job or have available to test.
       - name: Upload Packages as Artifacts
         uses: actions/upload-artifact@v3
-        if: ${{ env.IS_PR == 'false' }}
+        if: ${{ env.IS_PR == 'false' || github.event.pull_request.head.repo.full_name != github.repository }}
         with:
           name: nuget-packages-${{ matrix.platform }}
           if-no-files-found: error