fix next start not working (#3608)

Co-authored-by: Nicolas Dorseuil <[email protected]>

Author: conico974

packages/gitbook/package.json

@@ -104,7 +104,8 @@
         "clean": "rm -rf ./.next && rm -rf ./public/~gitbook/static/icons && rm -rf ./public/~gitbook/static/math",
         "dev": "env-cmd --silent -f ../../.env.local next",
         "build": "next build",
-        "start": "next start",
+        "build:local": "GITBOOK_URL=http://localhost:3000 next build",
+        "start": "GITBOOK_URL=http://localhost:3000 next start",
         "build:cloudflare": "opennextjs-cloudflare build",
         "dev:cloudflare": "wrangler dev --port 8771 --env preview",
         "dev:cf:middleware": "wrangler dev --port 8771 --inspector-port 9230 --env dev --config ./openNext/customWorkers/middlewareWrangler.jsonc",