Merge "Extend the docs somewhat to avoid downloading unneeded prebuilts when doing an update." into main am: a27964c3ee am: 0eb1a78645 am: b126ada5c3 am: 4cff1941f5

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

Change-Id: I4213d29fbde8ba099599f3a8610b1a0164e1e5c5
Signed-off-by: Automerger Merge Worker <[email protected]>