test: skip webpack configuration on turbopack build error

Author: pieh

tests/fixtures/middleware/next.config.js

@@ -19,6 +19,15 @@ const nextConfig = {
 
     return config
   },
+  // turbopack becomes default for builds in Next 16. There is failure when webpack configuration is present
+  // without turbopack configuration, so we add a turbopack configuration here to ensure this fixture
+  // works with default build bundler for all tested versions
+  // see https://github.com/vercel/next.js/blob/ba5a0ca79944b4c8a59d80d677bfedaf0fef33d6/packages/next/src/lib/turbopack-warning.ts#L159-L177
+  turbopack: {
+    // there need to be some keys here, as empty object despite currently being suggesting is not actually allowing build to go through
+    // so we'll set root (which serves same purpose as outputFileTracingRoot more generally)
+    root: __dirname,
+  },
   outputFileTracingRoot: __dirname,
 }