Revert^2 "ART: Refactor typedef to using"

This reverts commit ee07743e03042c2ca36e0c9513847a9e7d2509f1.

Reason for revert: fixed attributes.

Bug: 32619234
Test: m test-art-host
Test: m test-art-target-gtest-unstarted_runtime_test
Change-Id: I6f0a775adfdf6ecd132b470f7c5446e949872e20
diff --git a/sigchainlib/sigchain_test.cc b/sigchainlib/sigchain_test.cc
index 53e1e40..bb99787 100644
--- a/sigchainlib/sigchain_test.cc
+++ b/sigchainlib/sigchain_test.cc
@@ -38,7 +38,7 @@
 #include "sigchain.h"
 
 #if !defined(__BIONIC__)
-typedef sigset_t sigset64_t;
+using sigset64_t = sigset_t;
 
 static int sigemptyset64(sigset64_t* set) {
   return sigemptyset(set);