Add gradle build

.gitlab-ci.yml

@@ -79,3 +79,11 @@ test:
       - ./gradlew test
     after_script:
         - awk -F"," '{ instructions += $4 + $5; covered += $5 } END { print covered, "/", instructions, " instructions covered"; print 100*covered/instructions, "% covered" }' /app/target/site/jacoco/jacoco.csv
+
+build:
+  stage: build
+  only:
+    - branches
+    - tags
+  script:
+    - ./gradlew build
\ No newline at end of file