Update build workflow to enable submodule checkout and simplify build command

.github/workflows/build.yml

@@ -2,6 +2,9 @@ name: Manuelles Build mit ISE
 
 on:
   workflow_dispatch:
+  push:
+    branches:
+      - main
 
 jobs:
   build:
@@ -9,9 +12,11 @@ jobs:
     steps:
       - name: Checkout
         uses: actions/checkout@v2
+        with:
+            submodules: true
 
       - name: Build
         run: |
           cd "$GITHUB_WORKSPACE/build"
-          make trace
+          make