patch 8.2.3778: lambda debug test fails in some configurations

Problem:    Lambda debug test fails in some configurations.
Solution:   Check feature in a legacy function.
diff --git a/src/testdir/test_vim9_script.vim b/src/testdir/test_vim9_script.vim
index ccbdc70..58cf020 100644
--- a/src/testdir/test_vim9_script.vim
+++ b/src/testdir/test_vim9_script.vim
@@ -4634,9 +4634,14 @@
   CheckDefExecAndScriptFailure(lines, 'some error continued', 1)
 enddef
 
-def Test_debug_with_lambda()
+func Test_debug_with_lambda()
   CheckRunVimInTerminal
 
+  " call indirectly to avoid compilation error for missing functions
+  call Run_Test_debug_with_lambda()
+endfunc
+
+def Run_Test_debug_with_lambda()
   var lines =<< trim END
       vim9script
       def Func()