ci: clang-tidy: run on PRs from forks

Author: atkassen

.github/workflows/clang-tidy.yml

@@ -40,6 +40,7 @@ jobs:
         with:
           ref: ${{ github.event.pull_request.head.ref }}
           fetch-depth: 0
+          repository: ${{ github.event.pull_request.head.repo.full_name }}
 
       - name: Install clang
         run: |