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

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

Change-Id: I2802a3cab6943606a848948add4ceb4bad87ec95
Signed-off-by: Automerger Merge Worker <[email protected]>