[lworld] RFR: 8376103: [lworld] Basic Zero support [v2]

[Aleksey Shipilev]

> On the way to stabilizing Valhalla for inclusion into mainline, we want to have Zero builds at least buildable and lightly runnable, e.g. for creating their own CDS archives. There is likely to be some bugtail to pass all the tests, this is out of scope for this basic support. We need to pull some fixes from mainline to make this work going smoother.
> 
> I have also enabled Zero Hotspot build in GHA back to keep it buildable.
> 
> Additional testing:
>  - [x] Linux x86_64 zero fastdebug, build works
>  - [x] Linux x86_64 zero fastdebug, bootcycle build works

Aleksey Shipilev has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains three additional commits since the last revision:

 - Merge branch 'lworld' into JDK-8376103-zero-support
 - Build works
 - Basic Zero build is working

-------------

Changes:
  - all: https://git.openjdk.org/valhalla/pull/1943/files
  - new: https://git.openjdk.org/valhalla/pull/1943/files/26031d86..c8e1f7b0

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=valhalla&pr=1943&range=01
 - incr: https://webrevs.openjdk.org/?repo=valhalla&pr=1943&range=00-01

  Stats: 39448 lines in 690 files changed: 24647 ins; 9077 del; 5724 mod
  Patch: https://git.openjdk.org/valhalla/pull/1943.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1943/head:pull/1943

PR: https://git.openjdk.org/valhalla/pull/1943