Red Hat build of Keycloak startup fails with java.lang.UnsupportedClassVersionError

Issue

• Starting Red Hat build of Keycloak fails with the following error:

 ./kc.sh start-dev
Exception in thread "main" java.lang.UnsupportedClassVersionError: org/keycloak/quarkus/runtime/KeycloakMain 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
    at java.base/java.lang.ClassLoader.defineClass1(Native Method)
    at java.base/java.lang.ClassLoader.defineClass(ClassLoader.java:1017)
    at io.quarkus.bootstrap.runner.RunnerClassLoader.loadClass(RunnerClassLoader.java:105)
    at io.quarkus.bootstrap.runner.RunnerClassLoader.loadClass(RunnerClassLoader.java:65)
    at io.quarkus.bootstrap.runner.QuarkusEntryPoint.doRun(QuarkusEntryPoint.java:60)
    at io.quarkus.bootstrap.runner.QuarkusEntryPoint.main(QuarkusEntryPoint.java:32)