skip build tags for fork PRs

Author: manvkaur

eng/ci/public-build.yml

@@ -38,6 +38,10 @@ extends:
           enabled: true
         runSourceLanguagesInSourceAnalysis: true
 
+    settings:
+      # PR's from forks do not have sufficient permissions to set tags.
+      skipBuildTagsForGitHubPullRequests: ${{ variables['System.PullRequest.IsFork'] }}
+
     stages:
       - stage: Build
         variables: