Add script to fetch OpenJDK 21 prebuilts am: f849b278a3

Original change: https://android-review.googlesource.com/c/platform/prebuilts/jdk/jdk21/+/2850965

Change-Id: Ie60c9d45580d79acce7ae636262a731270eff0d7
Signed-off-by: Automerger Merge Worker <[email protected]>
tree: 8bb389927994679bd1327672cfa8b9fa1f540fa3
  1. linux-x86/
  2. BUILD.bazel
  3. manifest.xml
  4. update.sh