Tell the user if the binstub directory is not on their path.

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

Index: sdk/lib/_internal/pub/test/global/binstubs/warns_if_not_on_path.dart
diff --git a/sdk/lib/_internal/pub/test/global/binstubs/binstub_runs_precompiled_snapshot_test.dart b/sdk/lib/_internal/pub/test/global/binstubs/warns_if_not_on_path.dart
similarity index 60%
copy from sdk/lib/_internal/pub/test/global/binstubs/binstub_runs_precompiled_snapshot_test.dart
copy to sdk/lib/_internal/pub/test/global/binstubs/warns_if_not_on_path.dart
index cc2491155ebf24597df69bba625008864a0f3b0f..8ea5d2e347dd8e104ff46378fcf95d62104494c3 100644
--- a/sdk/lib/_internal/pub/test/global/binstubs/binstub_runs_precompiled_snapshot_test.dart
+++ b/sdk/lib/_internal/pub/test/global/binstubs/warns_if_not_on_path.dart
@@ -9,25 +9,20 @@ import '../../test_pub.dart';
 
 main() {
   initConfig();
-  integration("the binstubs runs a precompiled snapshot if present", () {
+  integration("warns if the binstub directory is not on the path", () {
     servePackages((builder) {
       builder.serve("foo", "1.0.0", pubspec: {
         "executables": {
-          "foo-script": "script"
+          "script": null
         }
       }, contents: [
         d.dir("bin", [
-          d.file("script.dart", "main(args) => print('ok');")
+          d.file("script.dart", "main(args) => print('ok \$args');")
         ])
       ]);
     });
 
-    schedulePub(args: ["global", "activate", "foo"]);
-
-    d.dir(cachePath, [
-      d.dir("bin", [
-        d.matcherFile("foo-script", contains("script.dart.snapshot"))
-      ])
-    ]).validate();
+    schedulePub(args: ["global", "activate", "foo"],
+        output: contains("is not on your path"));
   });
 }