AAPT2: Enable windows build and make sure it builds

Mingw32 4.8 is kind of picky with macros and some complicated template
stuff. Luckily there was another way to represent the
SFINAE code that works on all platforms. Yay!

Change-Id: Idc2e38f47bfdc57b394550bfa0f53cc0b825df25

tools/aapt2/java/JavaClassGenerator.cpp

@@ -318,7 +318,7 @@ void JavaClassGenerator::addMembersToStyleableClass(const StringPiece16& package
         }
 
         std::unique_ptr<IntMember> indexMember = util::make_unique<IntMember>(
-                sortedAttributes[i].fieldName, i);
+                sortedAttributes[i].fieldName, static_cast<uint32_t>(i));
 
         AnnotationProcessor* attrProcessor = indexMember->getCommentBuilder();