Next.Config.Ts Relative Imports Resolve Against Process.Cwd() Instead Of Config File Directory

In the SWC-based TypeScript configuration transpilation path, `requireFromString` creates a new Node.js Module instance without setting its `filename` property. As a result, Node's `Module._resolveLookupPaths` treats the module as if it were from the REPL and resolves relative imports against `process.cwd()` rather than the config file's directory.

1. Create a Next.js project with a next.config.ts that imports a local file (e.g., './src/headers'). 2. Install dependencies inside the project directory. 3. From the project directory, run `npx next build` (works). 4. From the parent directory, run `node app/node_modules/next/dist/bin/next build app` (fails with 'Cannot find module'). 5. Optionally create a file at the same relative path under the parent directory; the build succeeds but loads the wrong file from the working directory.

The fix is straightforward but should be verified with absolute paths to avoid issues if the filename is relative. Ensure that the filename passed to `requireFromString` is normalized to an absolute path. Regression testing should cover Windows path handling and scenarios where the config file is symlinked. Rollback is straightforward: remove the `m.filename = filename` line if the change causes unexpected module resolution side effects. No concurrency or multi-threading risks are expected since Node.js module loading is synchronous and single-threaded.