Ensure native rules find maven_project_jar in runfiles

Due to bazelbuild/bazel#15043, Bazel's native
rule such as `sh_test` do not pick up `files` in `DefaultInfo` for a
target in `data`. This can lead to the unexplicable absence of the jar
generated by `maven_project_jar` and hence `java_export` from runfiles.

Until the upstream bug has been fixed, this is worked around by adding
the files to `data_runfiles`.

private/rules/maven_project_jar.bzl

@@ -73,7 +73,13 @@ def _maven_project_jar_impl(ctx):
     )
 
     return [
-        DefaultInfo(files = depset([bin_jar])),
+        DefaultInfo(
+            files = depset([bin_jar]),
+            # Workaround for https://github.com/bazelbuild/bazel/issues/15043
+            # Bazel's native rule such as sh_test do not pick up 'files' in
+            # DefaultInfo for a target in 'data'.
+            data_runfiles = ctx.runfiles([bin_jar]),
+        ),
         OutputGroupInfo(
             maven_artifact = [bin_jar],
             maven_source = [src_jar],