Documentation issue: "C toolchain configuration" contains extremely outdated information

Documentation URL: https://docs.bazel.build/versions/master/cc-toolchain-config-reference.html

At the bottom:

This is a long list of features. The plan is to get rid of them once Crosstool in Starlark is done.

The linked issue was closed mid-2018. If the protobuf CROSSTOOL file is no longer supported, it would be good to remove all documentation specific to it, ideally replacing with up-to-date documentation of the current mechanism.

It'd be really really nice to have a link to a few functioning and up-to-date toolchain configs - ideally with CI tests on bazel to ensure they stay in sync with the latest bazel version.