fix node version to 12 in pipeline

.gitlab-ci.yml

@@ -1,5 +1,5 @@
 # image: weboaks/node-karma-protractor-chrome
-image: node:latest
+image: node:12.22.5
 
 stages:
   - build
@@ -10,6 +10,7 @@ stages:
 cache:
   paths:
     - node_modules/
+    - .yarn
 
 #pages:
 #  stage: pages
@@ -38,8 +39,9 @@ cache:
 
 build:
   stage: build
+  before_script:
+    - yarn
   script:
-    - yarn install --pure-lockfile
     - yarn run build:prod:demobliss
   cache:
     policy: pull