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

sdk/lib/_internal/pub_generated/test/global/binstubs/does_not_warn_if_on_path_test.dart

Index: sdk/lib/_internal/pub_generated/test/global/binstubs/does_not_warn_if_on_path_test.dart
diff --git a/sdk/lib/_internal/pub_generated/test/global/binstubs/does_not_warn_if_on_path_test.dart b/sdk/lib/_internal/pub_generated/test/global/binstubs/does_not_warn_if_on_path_test.dart
new file mode 100644
index 0000000000000000000000000000000000000000..0faa7bdbc518a0e627434f8960313601b77c1904
--- /dev/null
+++ b/sdk/lib/_internal/pub_generated/test/global/binstubs/does_not_warn_if_on_path_test.dart
@@ -0,0 +1,28 @@
+import 'dart:io';
+import 'package:path/path.dart' as p;
+import 'package:scheduled_test/scheduled_test.dart';
+import '../../descriptor.dart' as d;
+import '../../test_pub.dart';
+main() {
+  initConfig();
+  integration("does not warn if the binstub directory is on the path", () {
+    servePackages((builder) {
+      builder.serve("foo", "1.0.0", pubspec: {
+        "executables": {
+          "script": null
+        }
+      },
+          contents: [
+              d.dir("bin", [d.file("script.dart", "main(args) => print('ok \$args');")])]);
+    });
+    var binDir = p.dirname(Platform.executable);
+    var separator = Platform.operatingSystem == "windows" ? ";" : ":";
+    var path = "${Platform.environment["PATH"]}$separator$binDir";
+    schedulePub(
+        args: ["global", "activate", "foo"],
+        output: isNot(contains("is not on your path")),
+        environment: {
+      "PATH": path
+    });
+  });
+}