Add plugin build roles

Add two roles for building plugins:

copy-plugin-deps simply copies the external_plugin_deps.bzl file
into place if it exists.

bazelisk-build is a general bazelisk build role.  In this case,
we use it to build a plugin.

Change-Id: I7f9aa59c4f977edda15b40b73ae8e5c682de34a3
10 files changed
tree: 1951194ed201ec25fd213288f4440158c1bd2f85
  1. playbooks/
  2. roles/
  3. zuul.d/
  4. .gitreview
  5. LICENSE
  6. README