Store the async-await compiled pub code directly in the repo.

sdk/lib/_internal/pub_generated/test/run/runs_the_script_in_checked_mode_test.dart

+import 'package:scheduled_test/scheduled_test.dart';
+import '../descriptor.dart' as d;
+import '../test_pub.dart';
+const SCRIPT = """
+main() {
+  int a = true;
+}
+""";
+main() {
+  initConfig();
+  integration('runs the script in checked mode by default', () {
+    d.dir(
+        appPath,
+        [d.appPubspec(), d.dir("bin", [d.file("script.dart", SCRIPT)])]).create();
+    schedulePub(
+        args: ["run", "script"],
+        error: contains("'bool' is not a subtype of type 'int' of 'a'"),
+        exitCode: 255);
+  });
+}