CI: add coverage parsing to the job

It works only if enabled via CI/CD Settings. More info available at
https://docs.gitlab.com/ee/user/project/pipelines/settings.html#test-coverage-parsing.

The parsing regex was tested on my GitLab forked project.

.gitlab-ci.yml

@@ -83,6 +83,8 @@ test:
 coverage:
   <<: *save_build_logs
   stage: test
+  variables:
+    coverage: '/^Lines:.\d+.\d+.(\d+\.\d+\%)/'
 
   script:
     - *environment_information
@@ -96,6 +98,11 @@ coverage:
     - ninja -C _build test
     - ninja -C _build coverage-html
 
+    # Parse the report to get the coverage result
+    - |
+      echo == Coverage ==
+      sed -e 's/<[^>]*>//g' _build/meson-logs/coveragereport/index.html | tr -d ' \t' | grep -A3 -P '^Lines:$'  | tr '\n' ' '; echo
+
 ##
 # Stage: Delivery
 #