clarified invocation of isabelle.setup.Setup: -classpath allows multiple jars, as required for scala3;

--- a/lib/scripts/getsettings	Thu Mar 31 22:40:34 2022 +0200
+++ b/lib/scripts/getsettings	Fri Apr 01 10:55:32 2022 +0200
@@ -130,7 +130,7 @@
 fi
 
 if [ -e "$ISABELLE_SETUP_JAR" ]; then
-  ISABELLE_SETUP_CLASSPATH="$(isabelle_java java -jar "$(platform_path "$ISABELLE_SETUP_JAR")" classpath)"
+  ISABELLE_SETUP_CLASSPATH="$(isabelle_jdk java -classpath "$(platform_path "$ISABELLE_SETUP_JAR")" isabelle.setup.Setup classpath)"
 fi
 
 set +o allexport