ci: fix submodules

Author: facchinm

.github/workflows/compile-examples.yml

@@ -66,6 +66,8 @@ jobs:
     steps:
       - name: Checkout repository
         uses: actions/checkout@v2
+        with:
+          submodules: recursive
 
       # The source files are in a subfolder of the ArduinoCore-API repository, so it's not possible to clone it directly to the final destination in the core
       - name: Checkout ArduinoCore-API