util: fix compilation on macos

timespec_get() is not available on macos, we need to pull in the
include/c11/threads_posix.h helper.

Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=103674
Fixes: e2d761de03 ("util: drop final reference to p_compiler.h")
Reviewed-by: Eric Engestrom <eric.engestrom@intel.com>

src/util/u_queue.c

@@ -26,7 +26,7 @@
 
 #include "u_queue.h"
 
-#include <time.h>
+#include "c11/threads.h"
 
 #include "util/os_time.h"
 #include "util/u_string.h"