Run kernel CMock unit tests when they are changed. (#531)

* Run kernel unit tests in a github action only when Unit Test files change

.github/workflows/kernel-unit-tests.yml

@@ -0,0 +1,41 @@
+name: Kernel Unit Tests
+on:
+  push:
+    paths:
+    - 'FreeRTOS/Test/CMock/**'
+
+jobs:
+  run:
+    runs-on: ubuntu-latest
+    steps:
+    - name: Checkout Repository
+      uses: actions/checkout@v2
+      with:
+        submodules: 'recursive'
+        fetch-depth: 5
+    - name: Setup Python
+      uses: actions/setup-python@master
+      with:
+        python-version: 3.8
+    - name: Install packages
+      run: |
+          sudo apt-get install lcov cflow ruby doxygen build-essential unifdef
+    - name: Run Unit Tests with ENABLE_SANITIZER=1
+      run: |
+          make -C FreeRTOS/Test/CMock clean
+          make -C FreeRTOS/Test/CMock ENABLE_SANITIZER=1 run_col_formatted
+    - name: Run Unit Tests for coverage
+      run: |
+          make -C FreeRTOS/Test/CMock clean
+          make -C FreeRTOS/Test/CMock lcovhtml
+          lcov --config-file FreeRTOS/Test/CMock/lcovrc --summary FreeRTOS/Test/CMock/build/cmock_test.info > FreeRTOS/Test/CMock/build/cmock_test_summary.txt
+    - name: Archive code coverage data
+      uses: actions/upload-artifact@v2
+      with:
+        name: coverage-data
+        path: FreeRTOS/Test/CMock/build/cmock_test*
+    - name: Archive code coverage html report
+      uses: actions/upload-artifact@v2
+      with:
+        name: coverage-report
+        path: FreeRTOS/Test/CMock/build/coverage