The Starlark code was moved into the fuchsia.git tree with the https://fuchsia-review.git.corp.google.com/c/fuchsia/+/793913 commit.
The rules can be found at https://cs.opensource.google/fuchsia/fuchsia/+/main:build/bazel_sdk
This file still contains the scripts and tools directories since they are being used for OOT repositories. They will be moved to another repo at a later time.