Add build-ios constraint

.gitlab-ci.yml

 stages:
 - build
 
-build:
+build-apk:
+  except:
+  - ios-build
   variables: 
     LANG: en_US.UTF-8
   stage: build
@@ -14,3 +16,14 @@ build:
     - cp $HOME/key.properties ./android/key.properties
     - make build-android
 
+build-ios:
+  only:
+  - ios-build
+  variables: 
+    LANG: en_US.UTF-8
+  stage: build
+  tags:
+    - macos 
+  script:
+    - make build-ios
+