Update CI script to pull submodules before build

.github/workflows/cmake.yml

@@ -17,6 +17,9 @@ jobs:
     steps:
     - uses: actions/checkout@v2
 
+    - name: Checkout submodules
+      run: git submodule update --init
+
     - name: Create Build Environment
       # Some projects don't allow in-source building, so create a separate build directory
       # We'll use this as our working directory for all subsequent commands