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

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

+import '../descriptor.dart' as d;
+import '../test_pub.dart';
+const SCRIPT = """
+main(List<String> args) {
+  print(args.join(" "));
+}
+""";
+main() {
+  initConfig();
+  integration('passes arguments to the spawned script', () {
+    d.dir(
+        appPath,
+        [d.appPubspec(), d.dir("bin", [d.file("args.dart", SCRIPT)])]).create();
+    var pub = pubRun(args: ["args", "--verbose", "-m", "--", "help"]);
+    pub.stdout.expect("--verbose -m -- help");
+    pub.shouldExit();
+  });
+}