Build instructions fail

[bruderjakob17]

I tried to build Walnut by running ./build.sh, but the following error is shown:

Building Walnut. To run tests, add the -t flag to the command.
Downloading https://services.gradle.org/distributions/gradle-7.5.1-bin.zip
...........10%............20%...........30%............40%...........50%............60%...........70%............80%...........90%............100%

Welcome to Gradle 7.5.1!

Here are the highlights of this release:
 - Support for Java 18
 - Support for building with Groovy 4
 - Much more responsive continuous builds
 - Improved diagnostics for dependency resolution

For more details see https://docs.gradle.org/7.5.1/release-notes.html

Starting a Gradle Daemon (subsequent builds will be faster)

FAILURE: Build failed with an exception.

* What went wrong:
A problem occurred configuring root project 'Walnut'.
> Could not open cp_proj generic class cache for build file '/home/jakob/opt/Walnut/build.gradle' (/root/.gradle/caches/7.5.1/scripts/c3z8tlvdbsfe7otjnai08oslm).
   > BUG! exception in phase 'semantic analysis' in source unit '_BuildScript_' Unsupported class file major version 65

* Try:
> Run with --stacktrace option to get the stack trace.
> Run with --info or --debug option to get more log output.
> Run with --scan to get full insights.

* Get more help at https://help.gradle.org

BUILD FAILED in 29s
Press enter to continue

My Java version is openjdk 21.0.8 2025-07-15.

[jn1z]

I just happened to see this... the build script here can't handle JDK 21, although it might be able to handle JDK 17.

Better is to use the newest version of Walnut, see: https://github.com/Walnut-Theorem-Prover/Walnut and https://github.com/Walnut-Theorem-Prover