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

sdk/lib/_internal/pub_generated/test/build/includes_dart_files_from_dependencies_in_debug_test.dart

+import 'package:scheduled_test/scheduled_test.dart';
+import '../descriptor.dart' as d;
+import '../test_pub.dart';
+main() {
+  initConfig();
+  integration("includes .dart files from dependencies in debug mode", () {
+    currentSchedule.timeout *= 3;
+    d.dir(
+        "foo",
+        [
+            d.libPubspec("foo", "0.0.1"),
+            d.dir(
+                "lib",
+                [
+                    d.file('foo.dart', 'foo() => print("hello");'),
+                    d.dir("sub", [d.file('bar.dart', 'bar() => print("hello");')])])]).create();
+    d.dir(appPath, [d.appPubspec({
+        "foo": {
+          "path": "../foo"
+        }
+      }),
+          d.dir(
+              "example",
+              [
+                  d.file("main.dart", 'myapp() => print("not entrypoint");'),
+                  d.dir(
+                      "sub",
+                      [d.file("main.dart", 'myapp() => print("not entrypoint");')])])]).create();
+    schedulePub(
+        args: ["build", "--mode", "debug", "example"],
+        output: new RegExp(r'Built \d+ files to "build".'));
+    d.dir(
+        appPath,
+        [
+            d.dir(
+                'build',
+                [
+                    d.dir(
+                        'example',
+                        [
+                            d.file("main.dart", 'myapp() => print("not entrypoint");'),
+                            d.dir(
+                                'packages',
+                                [
+                                    d.dir(
+                                        'foo',
+                                        [
+                                            d.file('foo.dart', 'foo() => print("hello");'),
+                                            d.dir("sub", [d.file('bar.dart', 'bar() => print("hello");')])])]),
+                            d.dir(
+                                "sub",
+                                [
+                                    d.file("main.dart", 'myapp() => print("not entrypoint");'),
+                                    d.nothing("packages")])])])]).validate();
+  });
+}