[jdk21u-dev] RFR: 8348905: Add support to specify the JDK for compiling Jtreg tests

[SendaoYan]

Hi all,

This pull request contains a backport of commit [cbe9ec53](https://github.com/openjdk/jdk/commit/cbe9ec530fc248be74766ff6ff32761cd415a6f0) from the [openjdk/jdk](https://git.openjdk.org/jdk) repository. This backport support set to an alternative JDK directory that is different from the JDK running the tests through `JDK_FOR_COMPILE`.

Thanks!

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Commit messages:
 - Backport cbe9ec530fc248be74766ff6ff32761cd415a6f0

Changes: https://git.openjdk.org/jdk21u-dev/pull/1375/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=1375&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8348905
  Stats: 4 lines in 1 file changed: 4 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/1375.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/1375/head:pull/1375

PR: https://git.openjdk.org/jdk21u-dev/pull/1375