patch 8.0.1571: can't build without GUI

Problem:    Can't build without GUI.
Solution:   Adjust #ifdef for gui_find_menu().
diff --git a/src/menu.c b/src/menu.c
index c04cd49..58429dc 100644
--- a/src/menu.c
+++ b/src/menu.c
@@ -2462,6 +2462,7 @@
 }
 
 #if defined(FEAT_GUI_MSWIN) || defined(FEAT_GUI_GTK) \
+	|| defined(FEAT_TERM_POPUP_MENU) \
 	|| defined(FEAT_BEVAL_TIP) || defined(PROTO)
 /*
  * Given a menu descriptor, e.g. "File.New", find it in the menu hierarchy.