[jdk21u-dev] RFR: 8341097: GHA: Demote Mac x86 jobs to build only

[Aleksey Shipilev]

WIP on our way to switch to better MacOS runners.

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

Commit messages:
 - Backport d66737ea1cfd92bcb208ded4e64822d12760205d

Changes: https://git.openjdk.org/jdk21u-dev/pull/2383/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=2383&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8341097
  Stats: 11 lines in 1 file changed: 0 ins; 11 del; 0 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/2383.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/2383/head:pull/2383

PR: https://git.openjdk.org/jdk21u-dev/pull/2383