Run Gradle with JDK 17+

[wmdietl]

#106 task typecheck_jdk11 fails with:

FAILURE: Build failed with an exception.

* What went wrong:
java.lang.UnsupportedClassVersionError: aQute/bnd/gradle/BndBuilderPlugin has been compiled by a more recent version of the Java Runtime (class file version 61.0), this version of the Java Runtime only recognizes class file versions up to 55.0
> aQute/bnd/gradle/BndBuilderPlugin has been compiled by a more recent version of the Java Runtime (class file version 61.0), this version of the Java Runtime only recognizes class file versions up to 55.0

* 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.

eisop/checker-framework requires that Gradle is run on at least JDK 17.
CI setup for eisop/annotation-tools needs to be adapted to this.