buildSrc:test failing on JDKs before JDK 25

On JDK 21:

$ ./gradlew --version

------------------------------------------------------------
Gradle 9.2.0
------------------------------------------------------------

Build time:    2025-10-29 13:53:23 UTC
Revision:      d9d6bbce03b3d88c67ef5a0ff31f7ae5e332d6bf

Kotlin:        2.2.20
Groovy:        4.0.28
Ant:           Apache Ant(TM) version 1.10.15 compiled on August 25 2024
Launcher JVM:  21.0.9 (Azul Systems, Inc. 21.0.9+10-LTS)
Daemon JVM:    /Library/Java/JavaVirtualMachines/zulu-21.jdk/Contents/Home (no JDK specified, using current Java home)
OS:            Mac OS X 15.7.1 aarch64
$ ./gradlew assemble --rerun-tasks

> Task :buildSrc:test

MultiReleaseJarPluginTests > validateJar() FAILED
    java.lang.AssertionError at MultiReleaseJarPluginTests.java:143

4 tests completed, 1 failed

I see the same failure on JDK 17. On JDK 25 ./gradlew assemble passes.

This is with the main branch, git SHA 386c6ca. I'm seeing the same failure in CI on Linux.