Apparently the production #Bazel docs use the nightly build. I found `native.package_relative_label()` in the docs and was trying to use it but consistently failing. I tried to trace down when the function was added, and discovered it was merged _yesterday_. How's that for turnaround time?
https://bazel.build/rules/lib/native#package_relative_label
https://github.com/bazelbuild/bazel/commit/b859571804f2095caaf018b172b59c90f185fd51