[gtk/test.msvc] clipboard-client.c: Include necessary headers for Windows

[Chun-wei Fan <fanchunwei src gnome org>]

commit e56754d27c3bb244ecde77b30864b0211fc656a7
Author: Chun-wei Fan <fanchunwei src gnome org>
Date:   Mon May 3 16:33:14 2021 +0800

    clipboard-client.c: Include necessary headers for Windows
    
    We need to include io.h and process.h for close() and exit(), as unistd.h may
    not be universally available.

 testsuite/gdk/clipboard-client.c | 4 ++++
 1 file changed, 4 insertions(+)
---
diff --git a/testsuite/gdk/clipboard-client.c b/testsuite/gdk/clipboard-client.c
index d9f8ff2f9d..b27da92205 100644
--- a/testsuite/gdk/clipboard-client.c
+++ b/testsuite/gdk/clipboard-client.c
@@ -4,6 +4,10 @@
 #include "wayland/gdkwayland.h"
 #endif
 
+#ifdef G_OS_WIN32
+#include <io.h>
+#include <process.h>
+#endif
 
 G_GNUC_NORETURN static void
 got_string_cb (GObject      *source,