[remix] Ensure the symlink directory exists in ensureSymlink() (#11205)

Customer reported an edge case where (in a monorepo) their project's
`package.json` did not list any dependencies (instead they are listed at
the root-level `package.json`) and this caused the `node_modules`
directory to not exist in the app subdirectory, causing
`ensureSymlink()` to fail.

packages/remix/src/utils.ts

@@ -359,6 +359,7 @@ async function ensureSymlink(
     }
   }
 
+  await fs.mkdir(symlinkDir, { recursive: true });
   await fs.symlink(relativeTarget, symlinkPath);
   debug(`Created symlink for "${pkgName}"`);
 }