Add (void) to some macros to satisfy compiler.

More modern versions of GCC (at least with aarch64) are warning about an
unused value in these locations. It's incorrect, but I guess that the
macro is confusing it.

Using a (void) tag is a little ugly but solves the problem.

Change-Id: If6ba5083ab6e501c81e7743ae1ed99a89565e57c
Reviewed-on: https://boringssl-review.googlesource.com/2810
Reviewed-by: Adam Langley <agl@google.com>
diff --git a/ssl/ssl_ciph.c b/ssl/ssl_ciph.c
index ed4e81b..fb8c047 100644
--- a/ssl/ssl_ciph.c
+++ b/ssl/ssl_ciph.c
@@ -1127,7 +1127,7 @@
     }
     *cipher_list_by_id = tmp_cipher_list;
     tmp_cipher_list = NULL;
-    sk_SSL_CIPHER_set_cmp_func(*cipher_list_by_id, ssl_cipher_ptr_id_cmp);
+    (void) sk_SSL_CIPHER_set_cmp_func(*cipher_list_by_id, ssl_cipher_ptr_id_cmp);
 
     sk_SSL_CIPHER_sort(*cipher_list_by_id);
   } else {