Add executable to Options interface to get the name of the executable used to execute the script.

tests/standalone/io/process_environment_test.dart

Index: tests/standalone/io/process_environment_test.dart
diff --git a/tests/standalone/io/process_environment_test.dart b/tests/standalone/io/process_environment_test.dart
index d5796eb6538e19bf5b6b2c20bd458b6ca4640d0e..26d5f4b23efa137363aff9dec6daa165dbb5187d 100644
--- a/tests/standalone/io/process_environment_test.dart
+++ b/tests/standalone/io/process_environment_test.dart
@@ -7,7 +7,7 @@
 #source('process_test_util.dart');
 
 runEnvironmentProcess(Map environment, name, callback) {
-  var dartExecutable = getDartFileName();
+  var dartExecutable = new Options().executable;
   var options = new ProcessOptions();
   options.environment = environment;
   var printEnv = 'tests/standalone/io/print_env.dart';