Get binstubs working on Windows.

sdk/lib/_internal/pub/test/global/binstubs/binstub_runs_executable_test.dart

Index: sdk/lib/_internal/pub/test/global/binstubs/binstub_runs_executable_test.dart
diff --git a/sdk/lib/_internal/pub/test/global/binstubs/binstub_runs_executable_test.dart b/sdk/lib/_internal/pub/test/global/binstubs/binstub_runs_executable_test.dart
index cc3fbdb9b76168d013a5680ca6176482b1529a76..30167b0e796234769d7ca6f6c59c3a4092a454dd 100644
--- a/sdk/lib/_internal/pub/test/global/binstubs/binstub_runs_executable_test.dart
+++ b/sdk/lib/_internal/pub/test/global/binstubs/binstub_runs_executable_test.dart
@@ -10,6 +10,7 @@ import 'package:scheduled_test/scheduled_test.dart';
 
 import '../../descriptor.dart' as d;
 import '../../test_pub.dart';
+import 'utils.dart';
 
 main() {
   initConfig();
@@ -29,7 +30,8 @@ main() {
     schedulePub(args: ["global", "activate", "foo"]);
 
     var process = new ScheduledProcess.start(
-        p.join(sandboxDir, cachePath, "bin/foo-script"), ["arg1", "arg2"],
+        p.join(sandboxDir, cachePath, "bin", binStubName("foo-script")),
+        ["arg1", "arg2"],
         environment: getEnvironment());
 
     process.stdout.expect("ok [arg1, arg2]");
@@ -52,7 +54,8 @@ main() {
     schedulePub(args: ["global", "activate", "-spath", "../foo"]);
 
     var process = new ScheduledProcess.start(
-        p.join(sandboxDir, cachePath, "bin/foo-script"), ["arg1", "arg2"],
+        p.join(sandboxDir, cachePath, "bin", binStubName("foo-script")),
+        ["arg1", "arg2"],
         environment: getEnvironment());
 
     process.stdout.expect("ok [arg1, arg2]");