unbreak unnecessary dependency on 64-bit atomics

This unbreaks builds on 32-bit arms and mipsen.
diff --git a/src/tests/profile-handler_unittest.cc b/src/tests/profile-handler_unittest.cc
index 3531bef..06efb34 100644
--- a/src/tests/profile-handler_unittest.cc
+++ b/src/tests/profile-handler_unittest.cc
@@ -39,8 +39,8 @@
 // unregister callbacks without deadlocking. Thus this
 // "infrastructure" below.
 namespace {
-std::atomic<uint64_t> allocate_count;
-std::atomic<uint64_t> free_count;
+std::atomic<intptr_t> allocate_count;
+std::atomic<intptr_t> free_count;
 // We also "frob" this lock down in BusyThread.
 Mutex allocate_lock;