Nullness checker not working Windows

[wadoon]

Description

The checkerframework can not find the stubs on Windows:

Hinweis: The Checker Framework is tested with JDK 8, 11, 17, and 21. You are using version 24.
Warnung: KeyForSubchecker did not find annotation file or directory C:\Users\weigl\IdeaProjects\key/key.util/src/main/checkerframework:permit-nullness-assertion-exception.astub on classpath or within directory C:\Users\weigl\IdeaProjects\key\key.util\src\main
Warnung: InitializationFieldAccessSubchecker did not find annotation file or directory C:\Users\weigl\IdeaProjects\key/key.util/src/main/checkerframework:permit-nullness-assertion-exception.astub on classpath or within directory C:\Users\weigl\IdeaProjects\key\key.util\src\main
Warnung: NullnessNoInitSubchecker did not find annotation file or directory C:\Users\weigl\IdeaProjects\key/key.util/src/main/checkerframework:permit-nullness-assertion-exception.astub on classpath or within directory C:\Users\weigl\IdeaProjects\key\key.util\src\main
Warnung: NullnessChecker did not find annotation file or directory C:\Users\weigl\IdeaProjects\key/key.util/src/main/checkerframework:permit-nullness-assertion-exception.astub on classpath or within directory C:\Users\weigl\IdeaProjects\key\key.util\src\main

Reproducible

Is the issue reproducible?

always

Steps to reproduce

1. Enable nullness checking in settings.gradle
2. gradle classes

Additional information

I already tried to figure out if the path separator misleads checkerframework, by using the following snippet w/o success.

def stubs = [
        "$projectDir/src/main/checkerframework:permit-nullness-assertion-exception.astub",
        "checker.jar/junit-assertions.astub",
]

def stubString = stubs.join(File.pathSeparator)