[JVM] Don't let signal(SIGINT) break the REPL
[JVM] Don't let signal(SIGINT) break the REPL

The support for signals on the JVM backend is only rudimentary. The
recently introduced (cf7b4f18da) call to signal(SIGINT).tap doesn't
work on the JVM backend:

  $ ./rakudo -e 'signal(SIGINT).tap'
  Exception in thread "Thread-3" java.lang.NullPointerException
          at org.raku.nqp.runtime.IOOps$SigRunnable.run(IOOps.java:31)
          at java.base/java.lang.Thread.run(Thread.java:834)

It seems best to just skip the problematic command.

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