fix and check syntax

.github/workflows/build.yaml

@@ -11,6 +11,9 @@ jobs:
     steps:
       - uses: actions/checkout@v4
 
+      - name: Run ShellCheck on GHA config
+        uses: saleor/shellcheck-gha@v0
+
       - name: Prepare OCI metadata
         id: meta
         uses: docker/metadata-action@v5
@@ -171,7 +174,7 @@ jobs:
           while [[ -z $(kubectl -n "${ns}" get "${service}" -o jsonpath="{.status.loadBalancer.ingress}" 2>/dev/null) ]]; do
             if [ "$attempt" -lt "10" ]; then
               info "Waiting for ${service} to obtain endpoint ..."
-              attempt=((attempt+1))
+              attempt=$((attempt+1))
               sleep 10
             else
               die "ERROR: Timeout waiting for ${service} to obtain endpoint!"