[COMMIT osv master] tst-async.cc: include <thread> to silence error in GCC 11

[Commit Bot]

From: Waldemar Kozaczuk <jwkoz...@gmail.com>
Committer: Waldemar Kozaczuk <jwkoz...@gmail.com>
Branch: master

tst-async.cc: include <thread> to silence error in GCC 11

New GCC 11 throws errors when compiling tst-async.cc possibly
caused by removed include of <thread> in some of the headers directly
or indirectly included by tst-async.cc. To fix this we explicitly
include <thread> in tst-async.cc.

Refs #1144

Signed-off-by: Waldemar Kozaczuk <jwkoz...@gmail.com>

---
diff --git a/tests/tst-async.cc b/tests/tst-async.cc
--- a/tests/tst-async.cc
+++ b/tests/tst-async.cc
@@ -13,6 +13,7 @@
#include <osv/migration-lock.hh>
#include <boost/test/unit_test.hpp>
#include <future>
+#include <thread>

using namespace osv::clock::literals;
using namespace async;