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

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

+import 'package:scheduled_test/scheduled_test.dart';
+import 'package:path/path.dart' as path;
+import '../descriptor.dart' as d;
+import '../test_pub.dart';
+main() {
+  initConfig();
+  integration("handles long relative paths", () {
+    currentSchedule.timeout *= 3;
+    d.dir(
+        "some_long_dependency_name",
+        [
+            d.libPubspec("foo", "0.0.1"),
+            d.dir("lib", [d.file("foo.txt", "foo")])]).create();
+    var longPath = "";
+    for (var i = 0; i < 100; i++) {
+      longPath = path.join(longPath, "..", "some_long_dependency_name");
+    }
+    d.dir(appPath, [d.appPubspec({
+        "foo": {
+          "path": longPath
+        }
+      }), d.dir("web", [d.file("index.html", "html")])]).create();
+    schedulePub(
+        args: ["build"],
+        output: new RegExp(r'Built 2 files to "build".'));
+    d.dir(
+        appPath,
+        [
+            d.dir(
+                'build',
+                [
+                    d.dir(
+                        'web',
+                        [
+                            d.file("index.html", "html"),
+                            d.dir('packages', [d.dir('foo', [d.file('foo.txt', 'foo')])])])])]).validate();
+  });
+}