Merge "Extend the docs somewhat to avoid downloading unneeded prebuilts when doing an update." into main am: a27964c3ee

Original change: https://android-review.googlesource.com/c/platform/prebuilts/runtime/+/2785966

Change-Id: I4fce1b7c8b799ebd08dd8f9d1ba15ca0cee9f8d4
Signed-off-by: Automerger Merge Worker <[email protected]>