Add back in the analysis server training.

Change-Id: I6c7349d0df68e18e960bcc071aec40fd9cb8a224
Reviewed-on: https://dart-review.googlesource.com/66803
Reviewed-by: Zach Anderson <zra@google.com>
Reviewed-by: Alexander Aprelev <aam@google.com>
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Commit-Queue: Devon Carew <devoncarew@google.com>

utils/analysis_server/BUILD.gn

@@ -8,6 +8,7 @@ application_snapshot("analysis_server") {
   dart_version = 2
   main_dart = "../../pkg/analysis_server/bin/server.dart"
   training_args = [
-    "--help"
+    "--train-using=" + rebase_path("../../pkg/analyzer_cli"),
+    "--sdk=" + rebase_path("../../sdk/")
   ]
 }