Caching hides build failure on main

[mpkorstanje]

Steps to reproduce

For #3718 the https://github.com/junit-team/junit5/actions/runs/10656241470/job/29534673831 and for #3941 the https://github.com/junit-team/junit5/actions/runs/10646871397/job/29514199625 fail with:

> Task :platform-tooling-support-tests:test

JavaVersionsTests > java_default() FAILED
    org.opentest4j.AssertionFailedError: expected: <> but was: <WARNING: A restricted method in java.lang.System has been called
    WARNING: java.lang.System::load has been called by org.fusesource.jansi.internal.JansiLoader in an unnamed module (file:/home/runner/work/junit5/junit5/platform-tooling-support-tests/build/maven-distribution/apache-maven-3.9.8/lib/jansi-2.4.1.jar)
    WARNING: Use --enable-native-access=ALL-UNNAMED to avoid a warning for callers in this module
    WARNING: Restricted methods will be blocked in a future release unless native access is enabled
    >
        at app//org.junit.jupiter.api.AssertionFailureBuilder.build(AssertionFailureBuilder.java:151)
        at app//org.junit.jupiter.api.AssertionFailureBuilder.buildAndThrow(AssertionFailureBuilder.java:132)
        at app//org.junit.jupiter.api.AssertEquals.failNotEqual(AssertEquals.java:197)
        at app//org.junit.jupiter.api.AssertEquals.assertEquals(AssertEquals.java:182)
        at app//org.junit.jupiter.api.AssertEquals.assertEquals(AssertEquals.java:177)
        at app//org.junit.jupiter.api.Assertions.assertEquals(Assertions.java:1145)
        at app//platform.tooling.support.tests.JavaVersionsTests.execute(JavaVersionsTests.java:63)
        at app//platform.tooling.support.tests.JavaVersionsTests.java_default(JavaVersionsTests.java:46)

Yet on main 5f9eeb7 with https://github.com/junit-team/junit5/actions/runs/10653412771/job/29528480579 this passes:

 > Task :platform-tooling-support-tests:test FROM-CACHE

Presumably, because the build result was pulled from cache. But I don't think the failure is related to the changes in #3718 or #3941 so the caching would seem inappropriate here.

[marcphilipp]

Thanks for raising this! I've also noticed this and tracked down the root cause to differences between different builds of OpenJDK 24-ea. In 8665d6d, I've addressed this by tracking the exact Java runtime version as part of the cache key unless the default JDK (21 as of now) is used.