test/dlopen: use pthread_once directly

Signed-off-by: Austin Foxley <austinf@cetoncorp.com>

test/dlopen/libtest.c

@@ -2,12 +2,10 @@
 #include <pthread.h>
 #include <stdint.h>
 
-extern int __pthread_once(void);
-
 void dltest(uint32_t **value1, uint32_t **value2);
 void dltest(uint32_t **value1, uint32_t **value2)
 {
-	*value1 = (uint32_t *) __pthread_once;
+	*value1 = (uint32_t *) pthread_once;
 	*value2 = (uint32_t *) pthread_self;
 }