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

sdk/lib/_internal/pub_generated/test/snapshot/prints_errors_for_broken_snapshots_test.dart

+library pub_tests;
+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("prints errors for broken snapshot compilation", () {
+    servePackages((builder) {
+      builder.serve(
+          "foo",
+          "1.2.3",
+          contents: [
+              d.dir(
+                  "bin",
+                  [
+                      d.file("hello.dart", "void main() { no closing brace"),
+                      d.file("goodbye.dart", "void main() { no closing brace")])]);
+      builder.serve(
+          "bar",
+          "1.2.3",
+          contents: [
+              d.dir(
+                  "bin",
+                  [
+                      d.file("hello.dart", "void main() { no closing brace"),
+                      d.file("goodbye.dart", "void main() { no closing brace")])]);
+    });
+    d.appDir({
+      "foo": "1.2.3",
+      "bar": "1.2.3"
+    }).create();
+    pubGet(
+        error: allOf(
+            [
+                contains("Failed to precompile foo:hello"),
+                contains("Failed to precompile foo:goodbye"),
+                contains("Failed to precompile bar:hello"),
+                contains("Failed to precompile bar:goodbye")]),
+        exitCode: 0);
+    d.dir(
+        p.join(appPath, '.pub', 'bin'),
+        [
+            d.file('sdk-version', '0.1.2+3\n'),
+            d.dir(
+                'foo',
+                [d.nothing('hello.dart.snapshot'), d.nothing('goodbye.dart.snapshot')]),
+            d.dir(
+                'bar',
+                [
+                    d.nothing('hello.dart.snapshot'),
+                    d.nothing('goodbye.dart.snapshot')])]).validate();
+  });
+}