tests/clutter/interactive: Init backend and mutter context

As was with the tests run via meson test, for the interactive tests we
too need to configure the mutter backend and initialize things in order
to be able to run any tests.

https://gitlab.gnome.org/GNOME/mutter/merge_requests/932

src/tests/clutter/interactive/meson.build

@@ -83,6 +83,7 @@ executable('test-interactive',
   dependencies: [
     clutter_deps,
     libmutter_clutter_dep,
+    libmutter_dep,
     gdk_pixbuf_dep,
   ],
   install: false,

src/tests/clutter/interactive/test-main.c

@@ -1,8 +1,15 @@
+#include "config.h"
+
 #include <stdlib.h>
 #include <string.h>
 #include <glib.h>
 #include <gmodule.h>
 
+#include "backends/x11/nested/meta-backend-x11-nested.h"
+#include "core/main-private.h"
+#include "meta/main.h"
+#include "wayland/meta-wayland.h"
+#include "wayland/meta-xwayland.h"
 #include "test-unit-names.h"
 
 #define MAX_DESC_SIZE   72
@@ -119,6 +126,12 @@ main (int argc, char **argv)
 
   g_option_context_free (context);
 
+  meta_wayland_override_display_name ("mutter-test-display");
+  meta_xwayland_override_display_number (512);
+  meta_override_compositor_configuration (META_COMPOSITOR_TYPE_WAYLAND,
+                                          META_TYPE_BACKEND_X11_NESTED);
+  meta_init ();
+
   module = g_module_open (NULL, 0);
   if (!module)
     g_error ("*** Failed to open self for symbol lookup");