[gnome-builder] libide/webkit: add missing include guards

[Christian Hergert <chergert src gnome org>]

commit 556f6176eb9ba0a91795fe975110698085d43035
Author: Christian Hergert <chergert redhat com>
Date:   Fri Sep 16 16:01:11 2022 -0700

    libide/webkit: add missing include guards

 src/libide/webkit/ide-webkit-page.h | 4 ++++
 1 file changed, 4 insertions(+)
---
diff --git a/src/libide/webkit/ide-webkit-page.h b/src/libide/webkit/ide-webkit-page.h
index ecc1b7c1a..5b2504ea5 100644
--- a/src/libide/webkit/ide-webkit-page.h
+++ b/src/libide/webkit/ide-webkit-page.h
@@ -20,6 +20,10 @@
 
 #pragma once
 
+#if !defined (IDE_WEBKIT_INSIDE) && !defined (IDE_WEBKIT_COMPILATION)
+# error "Only <libide-webkit.h> can be included directly."
+#endif
+
 #include <libide-gui.h>
 
 #include "ide-html-generator.h"