Update cmake-multi-platform.yml

.github/workflows/cmake-multi-platform.yml

@@ -53,6 +53,8 @@ jobs:
 
     steps:
     - uses: actions/checkout@v3
+      with:
+      submodules: 'true'
 
     - name: Set reusable strings
       # Turn repeated input strings (such as the build output directory) into step outputs. These step outputs can be used throughout the workflow file.