better approach to file output for group.bzl rule (#311)
better approach to file output for group.bzl rule (#311)

This change mirrors what has already been done for passwd.bzl rule in
commit 0d6b0a387b1a04e3b987f9761d21a41b1edc8039.
bazelbuild/rules_docker,bazelbuild/rules_docker,bazelbuild/rules_docker,bazelbuild/rules_docker