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

[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

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Commit messages:
 - Build works
 - Basic Zero build is working

Changes: https://git.openjdk.org/valhalla/pull/1943/files
  Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=1943&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8376103
  Stats: 48 lines in 7 files changed: 30 ins; 0 del; 18 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