patch 8.2.3009: startup test may hang

Problem:    Startup test may hang.
Solution:   Do not run the test in the GUI.
diff --git a/src/testdir/test_startup.vim b/src/testdir/test_startup.vim
index 7e98591..a6e52ce 100644
--- a/src/testdir/test_startup.vim
+++ b/src/testdir/test_startup.vim
@@ -1302,6 +1302,8 @@
 endfunc
 
 func Test_echo_true_in_cmd()
+  CheckNotGui
+
   let lines =<< trim END
       echo v:true
       call writefile(['done'], 'Xresult')
@@ -1313,7 +1315,6 @@
   endif
   call delete('Xscript')
   call delete('Xresult')
-
 endfunc
 
 " vim: shiftwidth=2 sts=2 expandtab