Upgrade the Xcode to 11.1.0 on CircleCI

Fix #None

Author: Minggang Wang

.circleci/config.yml

@@ -8,7 +8,7 @@ jobs:
       CIRCLE_ARTIFACTS: /tmp/circleci-artifacts
       CIRCLE_TEST_REPORTS: /tmp/circleci-test-results
     macos:
-      xcode: 9.4.1
+      xcode: 11.1.0
     steps:
     - checkout
     - run: mkdir -p $CIRCLE_ARTIFACTS $CIRCLE_TEST_REPORTS