Use command on Windows that ends quickly.

tests/standalone/io/process_path_test.dart

Index: tests/standalone/io/process_path_test.dart
diff --git a/tests/standalone/io/process_path_test.dart b/tests/standalone/io/process_path_test.dart
index 649f07213e8ff69d0d43cdf63ea0c691d5df533a..03debe3a7a754ed78e49b64fa1943fec9c2e2218 100644
--- a/tests/standalone/io/process_path_test.dart
+++ b/tests/standalone/io/process_path_test.dart
@@ -10,10 +10,15 @@
 main() {
   // Pick an app that we expect to be on the PATH that returns 0 when run with
   // no arguments.
-  var executable = Platform.operatingSystem == 'windows' ? 'cmd.exe' : 'true';
+  var executable = 'true';
+  var args = [];
+  if (Platform.operatingSystem == 'windows') {
+    executable = 'cmd.exe';
+    args = ['/C', 'echo', '"ok"'];
+  }
 
   var options = new ProcessOptions();
-  Process.run(executable, []).then((result) {
+  Process.run(executable, args).then((result) {
     Expect.equals(0, result.exitCode);
   });
 }