ci: fast-forward to master/HEAD on all circle jobs (#18101)

This problem was introduced by a bad merge.

.circleci/config.yml

@@ -1,18 +1,31 @@
-defaults: &defaults
+# Configuration file for https://circleci.com/gh/angular/angular
+
+# Note: YAML anchors allow an object to be re-used, reducing duplication.
+# The ampersand declares an alias for an object, then later the `<<: *name`
+# syntax dereferences it.
+# See http://blog.daemonl.com/2016/02/yaml.html
+# To validate changes, use an online parser, eg.
+# http://yaml-online-parser.appspot.com/
+
+# Settings common to each job
+anchor_1: &job_defaults
   working_directory: ~/ng
   docker:
     - image: angular/ngcontainer
 
+# After checkout, rebase on top of master.
+# Similar to travis behavior, but not quite the same.
+# See https://discuss.circleci.com/t/1662
+anchor_2: &post_checkout
+  post: git pull --ff-only origin "refs/pull/${CI_PULL_REQUEST//*pull\//}/merge"
+
 version: 2
 jobs:
   lint:
-    <<: *defaults
+    <<: *job_defaults
     steps:
       - checkout:
-          # After checkout, rebase on top of master.
-          # Similar to travis behavior, but not quite the same.
-          # See https://discuss.circleci.com/t/1662
-          post: git pull --ff-only origin "refs/pull/${CI_PULL_REQUEST//*pull\//}/merge"
+          <<: *post_checkout
       - restore_cache:
           key: angular-{{ .Branch }}-{{ checksum "npm-shrinkwrap.json" }}
 
@@ -21,9 +34,10 @@ jobs:
       - run: ./node_modules/.bin/gulp lint
 
   build:
-    <<: *defaults
+    <<: *job_defaults
     steps:
-      - checkout
+      - checkout:
+          <<: *post_checkout
       - restore_cache:
           key: angular-{{ .Branch }}-{{ checksum "npm-shrinkwrap.json" }}