fix paths prefix

.gitlab-ci.yml

@@ -7,7 +7,7 @@ build:
   stage: build
   script:
     - npm install
-    - npm run build -- --prefix-paths ${CI_PAGES_URL}
+    - npm run build -- --prefix-paths
   artifacts:
     paths:
       - public

gatsby-config.js

 module.exports = {
+  pathPrefix:`.env.${process.env.CI_PAGES_URL}`,
   siteMetadata: {
     title: `Gatsby Default Starter`,
     description: `Kick off your next, great Gatsby project with this default starter. This barebones starter ships with the main Gatsby configuration files you might need.`,