nptl/tst-audit-threads: Switch to <support/test-driver.c>

The downstream version of test-skeleton.c does not include
<support/support.h> for backwards compatibility reasons, leading to a
compilation failure:

tst-audit-threads.c: In function 'do_test':
tst-audit-threads.c:87:3: error: implicit declaration of function 'xcalloc' [-Werror=implicit-function-declaration]
   threads = (pthread_t *) xcalloc (num_threads, sizeof(pthread_t));
   ^
tst-audit-threads.c:87:13: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
   threads = (pthread_t *) xcalloc (num_threads, sizeof(pthread_t));
             ^

diff --git a/nptl/tst-audit-threads.c b/nptl/tst-audit-threads.c
index e4bf433bd85f3715..42742d51e4bc06a3 100644
--- a/nptl/tst-audit-threads.c
+++ b/nptl/tst-audit-threads.c
@@ -25,19 +25,12 @@
    the relocation resolution caching code in the dynamic loader i.e.
    _dl_runtime_profile and _dl_profile_fixup.  */
 
+#include <support/support.h>
 #include <support/xthread.h>
 #include <strings.h>
 #include <stdlib.h>
 #include <sys/sysinfo.h>
 
-static int do_test (void);
-
-/* This test usually takes less than 3s to run.  However, there are cases that
-   take up to 30s.  */
-#define TIMEOUT 60
-#define TEST_FUNCTION do_test ()
-#include "../test-skeleton.c"
-
 /* Declare the functions we are going to call.  */
 #define externnum
 #include "tst-audit-threads.h"
@@ -95,3 +88,8 @@ do_test (void)
 
   return 0;
 }
+
+/* This test usually takes less than 3s to run.  However, there are cases that
+   take up to 30s.  */
+#define TIMEOUT 60
+#include <support/test-driver.c>