Improve smoke runner prerequisite diagnostics

.gitea/workflows/smoke.yml

@@ -15,11 +15,27 @@ jobs:
       - name: Verify runner prerequisites
         run: |
           set -euo pipefail
-          command -v bash >/dev/null
-          command -v curl >/dev/null
-          command -v gcc >/dev/null
-          command -v pkg-config >/dev/null
-          pkg-config --exists libnftables
+          require_cmd() {
+            if ! command -v "$1" >/dev/null 2>&1; then
+              echo "Missing required command: $1" >&2
+              exit 1
+            fi
+          }
+
+          require_cmd bash
+          require_cmd curl
+          require_cmd gcc
+          require_cmd pkg-config
+
+          if ! pkg-config --exists libnftables; then
+            echo "Missing libnftables pkg-config metadata on the runner host." >&2
+            echo "Install the system libnftables development package before running this workflow." >&2
+            exit 1
+          fi
+
+          echo "Runner prerequisites look good."
+          gcc --version | head -n 1
+          pkg-config --modversion libnftables
 
       - name: Install .NET SDK
         run: |