Make unit test more reliable, fix resulting failure

This unit test was not catching a defect on Mac/Linux because of the way that the compiler can optionally optimize out write operations that occur in the destructor.  Change the test to make use of a static member instead so as to avoid this.

src/autowiring/test/AutoSignalTest.cpp

@@ -626,18 +626,21 @@ namespace {
   class WiresInOuterScope {
   public:
     WiresInOuterScope(void) {
+      s_isConstructed = true;
       outer(&OuterType::sig) += [this] {
-        ASSERT_EQ(0xDEADBEEFC0FECAFE, magic);
+        ASSERT_TRUE(s_isConstructed) << "Signal handler invoked on an object that was already destroyed";
       };
     }
 
     ~WiresInOuterScope(void) {
-      magic = 0xEEEE0000FFFF0000;
+      s_isConstructed = false;
     }
 
     Autowired<OuterType> outer;
-    uint64_t magic = 0xDEADBEEFC0FECAFE;
+    static bool s_isConstructed;
   };
+
+  bool WiresInOuterScope::s_isConstructed = false;
 }
 
 TEST_F(AutoSignalTest, OuterPostDereference) {