Support directories other than "web" in pub build.

sdk/lib/_internal/pub/lib/src/command.dart

Index: sdk/lib/_internal/pub/lib/src/command.dart
diff --git a/sdk/lib/_internal/pub/lib/src/command.dart b/sdk/lib/_internal/pub/lib/src/command.dart
index a6823384bef9a502fccfe4701087a2d25e110909..e3dcab5ef072fac8cfb9c72cf00217044dcaeee4 100644
--- a/sdk/lib/_internal/pub/lib/src/command.dart
+++ b/sdk/lib/_internal/pub/lib/src/command.dart
@@ -186,7 +186,7 @@ and include the results in a bug report on http://dartbug.com/new.
         .then((_) {
       // Explicitly exit on success to ensure that any dangling dart:io handles
       // don't cause the process to never terminate.
-      return flushThenExit(0);
+      return flushThenExit(exit_codes.SUCCESS);
     });
   }