Refine build config

.gitlab-ci.yml

@@ -1,19 +1,21 @@
-image: swift:latest
+image: swift:5.0
 
-before_script:
-  - eval "$(curl -sL https://swiftenv.fuller.li/install.sh)"
+#before_script:
+  #- eval "$(curl -sL https://swiftenv.fuller.li/install.sh)"
 
 stages: 
-  - build
   - test
-
+  - build_release
+  
 build_project:
-  stage: build
+  stage: build_release
   script:
     - swift package reset
-    - swift build
+    - swift build -c release
   tags:
     - docker
+  only:
+    - master
 
 test_project:
   stage: test