Fix windows paths for invalid import errors (#45999)

Check for windows paths for the `server-only` and `client-only` build errors.

## Bug

- [ ] Related issues linked using `fixes #number`
- [ ] Integration tests added
- [ ] Errors have a helpful link attached, see [`contributing.md`](https://github.com/vercel/next.js/blob/canary/contributing.md)

## Feature

- [ ] Implements an existing feature request or RFC. Make sure the feature request has been accepted for implementation before opening a PR.
- [ ] Related issues linked using `fixes #number`
- [ ] [e2e](https://github.com/vercel/next.js/blob/canary/contributing/core/testing.md#writing-tests-for-nextjs) tests added
- [ ] Documentation added
- [ ] Telemetry added. In case of a feature if it's used or not.
- [ ] Errors have a helpful link attached, see [`contributing.md`](https://github.com/vercel/next.js/blob/canary/contributing.md)

## Documentation / Examples

- [ ] Make sure the linting passes by running `pnpm build && pnpm lint`
- [ ] The "examples guidelines" are followed from [our contributing doc](https://github.com/vercel/next.js/blob/canary/contributing/examples/adding-examples.md)

packages/next/src/build/webpack-config.ts

@@ -1996,7 +1996,7 @@ export default async function getBaseWebpackConfig(
             ]
           : []),
         {
-          test: /node_modules\/client-only\/error.js/,
+          test: /node_modules[/\\]client-only[/\\]error.js/,
           loader: 'next-invalid-import-error-loader',
           issuerLayer: WEBPACK_LAYERS.server,
           options: {
@@ -2005,7 +2005,7 @@ export default async function getBaseWebpackConfig(
           },
         },
         {
-          test: /node_modules\/server-only\/index.js/,
+          test: /node_modules[/\\]server-only[/\\]index.js/,
           loader: 'next-invalid-import-error-loader',
           issuerLayer: WEBPACK_LAYERS.client,
           options: {