[mutter] tests/wayland: Add a missing "include"

[Marge Bot <marge-bot src gnome org>]

commit c18ce8569e755b53c8cd484ef4f435944914ceca
Author: Dor Askayo <dor askayo gmail com>
Date:   Tue Jun 7 21:04:05 2022 +0300

    tests/wayland: Add a missing "include"
    
    This avoids the following error:
    
      ../src/tests/wayland-test-clients/dma-buf-scanout.c:100:5: error:
        implicit declaration of function ‘close’; did you mean ‘pclose’?
        [-Werror=implicit-function-declaration]
        100 |     close (buffer->dmabuf_fds[i]);
            |     ^~~~~
            |     pclose
    
    Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2458>

 src/tests/wayland-test-clients/dma-buf-scanout.c | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/src/tests/wayland-test-clients/dma-buf-scanout.c 
b/src/tests/wayland-test-clients/dma-buf-scanout.c
index 74b132c34a..25b9066965 100644
--- a/src/tests/wayland-test-clients/dma-buf-scanout.c
+++ b/src/tests/wayland-test-clients/dma-buf-scanout.c
@@ -46,6 +46,7 @@
 #include <fcntl.h>
 #include <gbm.h>
 #include <glib.h>
+#include <unistd.h>
 #include <wayland-client.h>
 
 #include "wayland-test-client-utils.h"