tests: Fix buffer test without NARG macro support

Signed-off-by: Andreas Schneider <asn@cryptomilk.org>

tests/unittests/torture_buffer.c

@@ -243,7 +243,10 @@ static void torture_buffer_pack_badformat(void **state){
 
     /* with additional format */
     rc = ssh_buffer_pack(buffer, "bb", b);
+#ifdef HAVE_GCC_NARG_MACRO
+    /* We can only detect errors if we have support for NARG macros */
     assert_int_equal(rc, SSH_ERROR);
+#endif
 
     /* unpack with missing format */
     ssh_buffer_reinit(buffer);