Make binstubs run snapshots directly when possible.

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

Index: sdk/lib/_internal/pub_generated/test/global/binstubs/binstub_runs_global_run_if_no_snapshot_test.dart
diff --git a/sdk/lib/_internal/pub_generated/test/global/binstubs/binstub_runs_global_run_if_no_snapshot_test.dart b/sdk/lib/_internal/pub_generated/test/global/binstubs/binstub_runs_global_run_if_no_snapshot_test.dart
new file mode 100644
index 0000000000000000000000000000000000000000..a3e7c0e86cd798c1247d2ce3c07c04a878d752af
--- /dev/null
+++ b/sdk/lib/_internal/pub_generated/test/global/binstubs/binstub_runs_global_run_if_no_snapshot_test.dart
@@ -0,0 +1,27 @@
+import 'package:scheduled_test/scheduled_test.dart';
+import '../../descriptor.dart' as d;
+import '../../test_pub.dart';
+main() {
+  initConfig();
+  integration("the binstubs runs pub global run if there is no snapshot", () {
+    d.dir("foo", [d.pubspec({
+        "name": "foo",
+        "executables": {
+          "foo-script": "script"
+        }
+      }),
+          d.dir("bin", [d.file("script.dart", "main() => print('ok');")])]).create();
+    schedulePub(
+        args: ["global", "activate", "--source", "path", "../foo"],
+        output: contains("Installed executable foo-script."));
+    d.dir(
+        cachePath,
+        [
+            d.dir(
+                "bin",
+                [
+                    d.matcherFile(
+                        "foo-script",
+                        contains("pub global run foo:script"))])]).validate();
+  });
+}