unbreak NativeCall for the JVM

The call to nqp::buildnativecall fails because it does not recognize the first arg as
an NativeCallInstance. Doing the clone always like before e167669
makes it work, see also: https://gist.github.com/FROGGS/0d4b5c771c7d9eb4f5b6

src/Perl6/Actions.nqp

@@ -2448,7 +2448,12 @@ class Perl6::Actions is HLL::Actions does STDActions {
         # Install PAST block so that it gets capture_lex'd correctly and also
         # install it in the lexpad.
         my $outer := $*W.cur_lexpad();
+#?if jvm
+        my $clone := 1; # Workaround to unbreak NativeCall on JVM.
+#?endif
+#?if !jvm
         my $clone := !($outer =:= $*UNIT);
+#?endif
         $outer[0].push(QAST::Stmt.new($block));
 
         # Install &?ROUTINE.