Attempting to let Bash interpolate the TAG variable.

.gitlab-ci.yml

@@ -25,7 +25,7 @@ build_release:
   except:
     - /^(?!master).+@/
   script:
-    - export TAG=`$CI_COMMIT_TAG | sed 's/v//g'`
+    - export TAG=$($CI_COMMIT_TAG | sed 's/v//g')
     - export MAIL_SERVICE_BIND_PORT=3000
     - export RABBITMQ_LISTENING_PORT=5672
     - export RABBITMQ_GUI_PORT=15672