Replace make with mage in CircleCI build

Updates #3969

Author: bep

.circleci/config.yml

@@ -14,8 +14,8 @@ jobs:
             command: |
                 git clone git@github.com:gohugoio/hugoDocs.git
                 cd hugo
-                make vendor
-                make check
+                mage vendor
+                mage check
       - persist_to_workspace:
           root: .
           paths: .