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/library/rsa.c b/library/rsa.c
index af1cef6..f3b1918 100644
--- a/library/rsa.c
+++ b/library/rsa.c
@@ -83,7 +83,7 @@
 #include "mbedtls/md.h"
 #endif
 
-#if defined(MBEDTLS_PKCS1_V15) && !defined(__OpenBSD__)
+#if defined(MBEDTLS_PKCS1_V15) && !defined(__OpenBSD__) && !defined(__NetBSD__)
 #include <stdlib.h>
 #endif
 
@@ -2590,7 +2590,7 @@
 #if defined(MBEDTLS_PKCS1_V15)
 static int myrand( void *rng_state, unsigned char *output, size_t len )
 {
-#if !defined(__OpenBSD__)
+#if !defined(__OpenBSD__) && !defined(__NetBSD__)
     size_t i;
 
     if( rng_state != NULL )
@@ -2603,7 +2603,7 @@
         rng_state = NULL;
 
     arc4random_buf( output, len );
-#endif /* !OpenBSD */
+#endif /* !OpenBSD && !NetBSD */
 
     return( 0 );
 }