ci: replace Travis with GitHub Actions

Minor cleanups in docs and build scripts

Change-Id: Icfab337d1b9c78f91ea0c47b65eb4dae6d589b18
diff --git a/.jenkins.d/30-coverage.sh b/.jenkins.d/30-coverage.sh
index c77175f..70c5c9b 100755
--- a/.jenkins.d/30-coverage.sh
+++ b/.jenkins.d/30-coverage.sh
@@ -2,29 +2,26 @@
 set -ex
 
 if [[ $JOB_NAME == *"code-coverage" ]]; then
+    # Generate an XML report (Cobertura format)
     gcovr --object-directory=build \
           --output=build/coverage.xml \
           --exclude="$PWD/tests" \
           --root=. \
           --xml
 
-    # Generate also a detailed HTML output, but using lcov (better results)
+    # Generate a detailed HTML report using lcov
     lcov --quiet \
          --capture \
          --directory . \
+         --exclude "$PWD/tests/*" \
          --no-external \
          --rc lcov_branch_coverage=1 \
-         --output-file build/coverage-with-tests.info
-
-    lcov --quiet \
-         --remove build/coverage-with-tests.info "$PWD/tests/*" \
-         --rc lcov_branch_coverage=1 \
          --output-file build/coverage.info
 
     genhtml --branch-coverage \
             --demangle-cpp \
             --legend \
-            --output-directory build/coverage \
+            --output-directory build/lcov \
             --title "ndn-nac unit tests" \
             build/coverage.info
 fi