AAPT2: Add library support

Change-Id: I307f56d9631784ab29ee4156d94886f9b2f25b30
diff --git a/tools/aapt2/Flag.h b/tools/aapt2/Flag.h
index 32f5f2c..4cadfc4 100644
--- a/tools/aapt2/Flag.h
+++ b/tools/aapt2/Flag.h
@@ -18,6 +18,8 @@
 
 void optionalSwitch(const StringPiece& name, const StringPiece& description, bool* result);
 
+void usageAndDie(const StringPiece& command);
+
 void parse(int argc, char** argv, const StringPiece& command);
 
 const std::vector<std::string>& getArgs();