Merge pull request #31 from mkroening/pr-no-push

ci: don't try to push image on PRs

Author: mkroening

.github/workflows/publish.yml

@@ -14,11 +14,12 @@ jobs:
     steps:
       - uses: docker/setup-buildx-action@v3
       - uses: docker/login-action@v3
+        if: github.event_name != 'pull_request'
         with:
           registry: ghcr.io
           username: ${{ github.actor }}
           password: ${{ secrets.GITHUB_TOKEN }}
       - uses: docker/build-push-action@v5
         with:
-          push: true
+          push: ${{ github.event_name != 'pull_request' }}
           tags: ghcr.io/hermit-os/hermit-toolchain:latest