Update unit-tests.yml

Added submodules to unit tests

Author: SergeAgeyev

.github/workflows/unit-tests.yml

@@ -25,6 +25,8 @@ jobs:
     steps:
       - name: Checkout repository
         uses: actions/checkout@v2
+        with:
+          submodules: 'true'
 
       - name: Relax some warings
         # run: echo 'add_compile_options(-Wno-unused-function)' >> ArduinoCore-API/test/CMakeLists.txt
@@ -51,4 +53,4 @@ jobs:
       #  with:
       #    token: ${{ secrets.CODECOV_TOKEN }}
       #    files: ${{ env.COVERAGE_DATA_PATH }}
-      #    fail_ci_if_error: true
+      #    fail_ci_if_error: true