Add locally built bootstrap JDK

The OpenJDK21 build requires a 20 or 21 bootstrap JDK, which we don't
yet have prebuilts for.  Check in this locally built OpenJDK21.
This will be replaced with a JDK built on the build servers once
they have completed a build bootstrapped from this JDK.

Bug: 302395149
Test: toolchain/jdk/build/build-openjdk21-linux.sh
Change-Id: Ib968726bc96e04c3ca9cb3b964a7be5d028244c1
425 files changed
tree: 43d8c350741889fc21c6e2a59a22eb378ed7b514
  1. linux-x86/
  2. BUILD.bazel
  3. manifest.xml
  4. update.sh