Fetch submodule:

NOTE: git submodule not used because AOSP doesn't allow it.

git clone https://fuchsia.googlesource.com/fuchsia-infra-bazel-rules fuchsia-build/third_party/fuchsia-infra-bazel-rules

Bootstrap:

fuchsia-build/third_party/fuchsia-infra-bazel-rules/scripts/bootstrap.sh

Fetch the toolchain (separately from the SDK):

./.cipd_client ensure -root fuchsia-build/toolchain/clang -ensure-file fuchsia-build/manifests/clang.ensure