Update .gitlab-ci.yml

.gitlab-ci.yml

 image: java:latest
 
 stages:
+  - assemble
   - build
   - javadoc
   - test
@@ -10,16 +11,23 @@ cache:
     - .gradle/wrapper
     - .gradle/caches
 
+assemble:
+  stage: assemble
+  script:
+    - ./gradlew assemble
+  artifacts:
+    paths:
+      - build/libs/*.jar
+    expire_in: 1 week
+    
 build:
   stage: build
   script:
-    - ./gradlew assemble
+    - ./gradlew build
   artifacts:
     paths:
       - build/libs/*.jar
     expire_in: 1 week
-  only:
-    - master
 
 javadoc:
   stage: javadoc