swift-reflection-test: silence tautological warning

PE/COFF does not permit weak linking semantics.  This means that the
expression `&symbol == NULL` is tautologically false.  In order to
support this semantic, the symbol needs to be dynamically looked up at
runtime.  Since the ObjC runtime is not in use on Windows currently,
just ignore this for the time being.  Silences a warning from clang
about the tautological comparison.

stdlib/tools/swift-reflection-test/swift-reflection-test.c

@@ -575,11 +575,16 @@ int main(int argc, char *argv[]) {
     printUsageAndExit();
 
   const char *BinaryFilename = argv[1];
-  
+
+#if defined(_WIN32)
+  // FIXME(compnerd) weak linking is not permitted on PE/COFF, we should fall
+  // back to GetProcAddress to see if the symbol is present.
+#else
   // swift_reflection_classIsSwiftMask is weak linked so we can work
   // with older Remote Mirror dylibs.
   if (&swift_reflection_classIsSwiftMask != NULL)
     swift_reflection_classIsSwiftMask = computeClassIsSwiftMask();
+#endif
 
   uint16_t Version = swift_reflection_getSupportedMetadataVersion();
   printf("Metadata version: %u\n", Version);