Plugin for the java8 runtime does not support building an image

I'm building some of the recently open sources resource providers,
```
[aidan@unknowne8d0fc9c5665 aws-codeartifact-domain]$ git config remote.origin.url
git@github.com:aws-cloudformation/aws-cloudformation-resource-providers-codeartifact.git
[aidan@unknowne8d0fc9c5665 aws-codeartifact-domain]$ git log | head -1
commit 161d785532c7f1d42d100989431efe437f411b17
[aidan@unknowne8d0fc9c5665 aws-codeartifact-domain]$ AWS_REGION=us-east-1 mvn clean package
...
[aidan@unknowne8d0fc9c5665 aws-codeartifact-domain]$ java -version
openjdk version "11.0.8" 2020-07-14
OpenJDK Runtime Environment 18.9 (build 11.0.8+10)
OpenJDK 64-Bit Server VM 18.9 (build 11.0.8+10, mixed mode, sharing)
```

Running,
```
[aidan@unknowne8d0fc9c5665 aws-codeartifact-domain]$ cfn build-image --image-name cfn-codeartifact-domain --executable target/aws-codeartifact-domain-handler-1.0-SNAPSHOT.jar
Plugin for the java8 runtime does not support building an image
```

What's wrong?