Tree shaking in middleware doesn't work

### Link to the code that reproduces this issue https://github.com/amannn/nextjs-bug-repro-middleware/commit/6c442b025f45b0f777fda6f32fc355e58bef1fb9 ### To Reproduce 1. Run `pnpm i && pnpm build` 2. See console output and analyzer output ### Current vs. Expected behavior **Console output:** ``` ƒ Middleware 1.07 MB ``` I'd expect `getMessages` to not be bundled into the middleware as it's not used there. See also the analyzer output:  ### Provide environment information ```bash Operating System: Platform: darwin Arch: x64 Version: Darwin Kernel Version 23.6.0: Mon Jul 29 21:13:00 PDT 2024; root:xnu-10063.141.2~1/RELEASE_X86_64 Available memory (MB): 16384 Available CPU cores: 12 Binaries: Node: 20.11.1 npm: 10.2.4 Yarn: 1.22.22 pnpm: 9.15.4 Relevant Packages: next: 15.1.5 // Latest available version is detected (15.1.5). eslint-config-next: N/A react: 19.0.0 react-dom: 19.0.0 typescript: 5.7.3 Next.js Config: output: N/A ``` ### Which area(s) are affected? (Select all that apply) Middleware ### Which stage(s) are affected? (Select all that apply) next build (local) ### Additional context _No response_