Use ctx.actions.run

[anchlovi]

Handles bazel 0.27 error message:

File "/private/var/tmp/_bazel_shacharan/8c22eb77db72f764bcc6d118ac354c04/external/com_github_johnynek_bazel_jar_jar/jar_jar.bzl", line 8, in _jar_jar_impl
		ctx.action(inputs = [ctx.file.rules, ctx.fi...], <4 more arguments>)
Use ctx.actions.run or ctx.actions.run_shell instead of ctx.action.

[johnynek]

This was a race with #12 no?

[johnynek]

Thank you for the PR!