Improve compiler/standards compatibility

Some don't like the old version, for reasons unclear.

Change-Id: I7adad6130d8fd6d6816140fe20ad7f5b6c444c8b
diff --git a/aos/ipc_lib/signalfd_test.cc b/aos/ipc_lib/signalfd_test.cc
index b4fe74b..a50e9f6 100644
--- a/aos/ipc_lib/signalfd_test.cc
+++ b/aos/ipc_lib/signalfd_test.cc
@@ -60,15 +60,15 @@
 // its signals.
 TEST(SignalFdDeathTest, ExternalUnblockSignal) {
   ::aos::testing::EnableTestLogging();
-  EXPECT_DEATH(
-      {
-        SignalFd signalfd({SIGUSR1});
-        sigset_t test_mask;
-        CHECK_EQ(0, sigemptyset(&test_mask));
-        CHECK_EQ(0, sigaddset(&test_mask, SIGUSR1));
-        PCHECK(sigprocmask(SIG_UNBLOCK, &test_mask, nullptr) == 0);
-      },
-      "Some other code unblocked one or more of our signals");
+  auto t = []() {
+    SignalFd signalfd({SIGUSR1});
+    sigset_t test_mask;
+    CHECK_EQ(0, sigemptyset(&test_mask));
+    CHECK_EQ(0, sigaddset(&test_mask, SIGUSR1));
+    PCHECK(sigprocmask(SIG_UNBLOCK, &test_mask, nullptr) == 0);
+  };
+  EXPECT_DEATH({ t(); },
+               "Some other code unblocked one or more of our signals");
 }
 
 }  // namespace testing