[jdk11u-dev] RFR: 8360816: [11u] Use default value for ProgramFiles(x86) in GHA [v2]

[Antonio Vieiro]

> A fix for [JDK-8360816](https://bugs.openjdk.org/browse/JDK-8360816). 
> 
> The `ProgramFiles(x86)` environment variable is not properly propagated to JTReg tests in JDK11, which makes the AOT compiler tests fail on the new `windows-2025` GHA runners, as manifested in the backport of [https://bugs.openjdk.org/browse/JDK-8358538](JDK-8358538).  
> 
> Propagating this environment variable to JTRegs may require creating devkits for Windows 2022, but previous attempts were discarded [JDK-8283723](https://bugs.openjdk.org/browse/JDK-8283723). 
> 
> This fix prints a warning message when this environment variable is not set, and then uses a default value (`C:\Program Files (x86)`) that makes it possible to run the AOT tests with these new `windows-2025` GHA runners.  If the `ProgramFiles(x86)` env variable is set the fix has no effect, ensuring the previous behaviour. If the proposed default value is incorrect the AOT tests will continue to fail as before.
> 
> The PR is on top of  https://github.com/openjdk/jdk11u-dev/pull/3052 to verify the fix works as intended with the new `windows-2025` GHA runners.

Antonio Vieiro 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.

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Changes:
  - all: https://git.openjdk.org/jdk11u-dev/pull/3056/files
  - new: https://git.openjdk.org/jdk11u-dev/pull/3056/files/4eee33e9..4eee33e9

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk11u-dev&pr=3056&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk11u-dev&pr=3056&range=00-01

  Stats: 0 lines in 0 files changed: 0 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk11u-dev/pull/3056.diff
  Fetch: git fetch https://git.openjdk.org/jdk11u-dev.git pull/3056/head:pull/3056

PR: https://git.openjdk.org/jdk11u-dev/pull/3056