[ddc] Fix batch mode argument parsing on Windows

This bug was introduced with
https://dart-review.googlesource.com/c/sdk/+/415280.

Fixes #60346.

Change-Id: I677145bcbf30b2c56eb061998be8ffd56f392dcd
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/416700
Reviewed-by: Nicholas Shahan <[email protected]>
Commit-Queue: Ömer Ağacan <[email protected]>

Author: osa1

pkg/dev_compiler/lib/ddc.dart

@@ -130,7 +130,7 @@ class _BatchHelper {
 
   Future<void> _doIteration(ParsedArguments batchArgs, String line) async {
     totalTests++;
-    var args = batchArgs.merge(splitLine(line));
+    var args = batchArgs.merge(splitLine(line, windows: Platform.isWindows));
 
     String outcome;
     try {