Merge branch 'stable-2.15' into stable-2.16

* stable-2.15:
  Upgrade bazlets to latest stable-2.15 to build with 2.15.12 API
  Upgrade bazlets to latest stable-2.14 to build with 2.14.19 API

Change-Id: Icbd291c1ae4f2adb5c9dd3198bec948954824517