update xcode to v11 (#1420)

kroikie · collinjackson · commit 9a64481a1344 · 2019-11-13T16:09:22.000-08:00
diff --git a/.cirrus.yml b/.cirrus.yml
@@ -68,7 +68,7 @@ task:
 task:
   use_compute_credits: $CIRRUS_USER_COLLABORATOR == 'true'
   osx_instance:
-    image: mojave-xcode-10.2-flutter
+    image: mojave-xcode-11.2.1-flutter
   setup_script:
     - pod repo update
   upgrade_script:
