Update ccpp.yml

.github/workflows/ccpp.yml

@@ -13,6 +13,10 @@ jobs:
 
     steps:
     - uses: actions/checkout@v2
+    - name: submodule
+      uses: srt32/git-actions@v0.0.3
+      with:
+        args: git submodule update --init
     - name: configure
       run: cmake .
     - name: make