Use DefaultInfo directly (#958)

Required for compatibility with
bazelbuild/bazel#20183

Author: tonyaiuto

pkg/mappings.bzl

@@ -257,7 +257,7 @@ def _pkg_files_impl(ctx):
     # Do file renaming
     for rename_src, rename_dest in ctx.attr.renames.items():
         # rename_src.files is a depset
-        rename_src_files = rename_src.files.to_list()
+        rename_src_files = rename_src[DefaultInfo].files.to_list()
 
         # Need to do a length check before proceeding. We cannot rename
         # multiple files simultaneously.

pkg/private/tar/tar.bzl

@@ -138,7 +138,7 @@ def _pkg_tar_impl(ctx):
     # The files attribute is a map of labels to destinations. We can add them
     # directly to the content map.
     for target, f_dest_path in ctx.attr.files.items():
-        target_files = target.files.to_list()
+        target_files = target[DefaultInfo].files.to_list()
         if len(target_files) != 1:
             fail("Each input must describe exactly one file.", attr = "files")
         mapping_context.file_deps.append(depset([target_files[0]]))