ci: unit_tests: collect coverage

Install both gcovr and ninja from pypi, so a single tool (pip) is used.

Signed-off-by: Marcin Niestroj <[email protected]>

.github/workflows/lint_build_unit_test.yml

@@ -46,9 +46,9 @@ jobs:
         with:
           submodules: 'recursive'
 
-      - name: Install ninja
+      - name: Install gcovr and ninja
         run: |
-          sudo apt install -y ninja-build
+          pip install gcovr ninja
 
       - name: Run unit tests
         run: |
@@ -59,6 +59,22 @@ jobs:
                 --output-on-failure                     \
                 --timeout 2
 
+      - name: Coverage
+        run: |
+          gcovr                                                         \
+            --gcov-ignore-parse-errors=negative_hits.warn_once_per_file \
+            --merge-mode-functions=separate                             \
+            --json coverage.json                                        \
+            build
+
+      - name: Upload test coverage artifacts
+        uses: actions/upload-artifact@v4
+        if: ${{ always() }}
+        with:
+          name: unit-test-coverage
+          path: |
+            coverage.json
+
   linux_build:
     runs-on: ubuntu-latest
     steps: