Use arc4random_buf instead of rand on NetBSD

Avoid old implementation of rand returning numbers with cyclical lower bits. Allow tests to pass.

Signed-off-by: gufe44 <gu981@protonmail.com>
diff --git a/tests/suites/helpers.function b/tests/suites/helpers.function
index 96e18da..e38df82 100644
--- a/tests/suites/helpers.function
+++ b/tests/suites/helpers.function
@@ -330,7 +330,7 @@
  */
 static int rnd_std_rand( void *rng_state, unsigned char *output, size_t len )
 {
-#if !defined(__OpenBSD__)
+#if !defined(__OpenBSD__) && !defined(__NetBSD__)
     size_t i;
 
     if( rng_state != NULL )
@@ -343,7 +343,7 @@
         rng_state = NULL;
 
     arc4random_buf( output, len );
-#endif /* !OpenBSD */
+#endif /* !OpenBSD && !NetBSD */
 
     return( 0 );
 }