fix: make route resolution imports root-relative if path.relative option is false (#13412)

It is necessary to adhere to this setting because rewrites that SvelteKit cannot see may otherwise lead to incorrect relative paths.

Example:
- route resolution request to _app/route.js
- rewrite to _app/route/foo.js
- SvelteKit only sees the later, returning a relative `import('../immutable/...`) which is wrong, because the actual relative path would be `import('./immutable/...)`

Author: dummdidumm

.changeset/sharp-games-rule.md

@@ -0,0 +1,5 @@
+---
+'@sveltejs/kit': patch
+---
+
+fix: make route resolution imports root-relative if `paths.relative` option is `false`

packages/kit/src/runtime/server/page/server_routing.js

@@ -1,4 +1,4 @@
-import { base, assets } from '__sveltekit/paths';
+import { base, assets, relative } from '__sveltekit/paths';
 import { text } from '../../../exports/index.js';
 import { s } from '../../../utils/misc.js';
 import { exec } from '../../../utils/routing.js';
@@ -47,6 +47,10 @@ function create_client_import(import_path, url) {
 		return `import('${assets}/${import_path}')`;
 	}
 
+	if (!relative) {
+		return `import('${base}/${import_path}')`;
+	}
+
 	// Else we make them relative to the server-side route resolution request
 	// to support IPFS, the internet archive, etc.
 	let path = get_relative_path(url.pathname, `${base}/${import_path}`);