The new builder will generate the mdbook and api docs, then
uploads them to GCS.
BUG=b:233411583
TEST=luci-auth context ./infra/recipes.py run build_docs
Change-Id: Ia22cdb20d73f9268db6299cd6f0875950d174b3f
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/3751832
Reviewed-by: Daniel Verkamp <dverkamp@chromium.org>
Tested-by: kokoro <noreply+kokoro@google.com>
