Make --write-results not appear in reproduction commands

Change-Id: Ibb492283c2b53762cb4f74da52c3f005cc282d85
Reviewed-on: https://dart-review.googlesource.com/c/78745
Reviewed-by: Alexander Thomas <athom@google.com>
Commit-Queue: Martin Kustermann <kustermann@google.com>
diff --git a/tools/testing/dart/options.dart b/tools/testing/dart/options.dart
index 6c72986..4bd3f1e 100644
--- a/tools/testing/dart/options.dart
+++ b/tools/testing/dart/options.dart
@@ -358,7 +358,8 @@
     'verbose',
     'write_debug_log',
     'write_test_outcome_log',
-    'write_result_log'
+    'write_result_log',
+    'write_results',
   ].toSet();
 
   /// Parses a list of strings as test options.