Add AIDL library to update_engine

Also move IApexService.h header to apex_handler_android.h, so that
consumer of ApexHandlerInterface do not need to see IApexService.h.

IApexService.h includes some binder_ndk headers, which includes
syslog.h, which defines LOG_INFO/LOG_WARNING. libchrome also defines
these macros, so including both libchrome and AIDL headers will cause
macro conflict.

Test: th
Bug: 227536004
Change-Id: Ia17d91cc878d106e9b2adeddafe35a71105e1663
diff --git a/aosp/apex_handler_interface.h b/aosp/apex_handler_interface.h
index b9b6c96..a0c1e9f 100644
--- a/aosp/apex_handler_interface.h
+++ b/aosp/apex_handler_interface.h
@@ -31,6 +31,7 @@
   virtual android::base::Result<uint64_t> CalculateSize(
       const std::vector<ApexInfo>& apex_infos) const = 0;
   virtual bool AllocateSpace(const std::vector<ApexInfo>& apex_infos) const = 0;
+  static std::unique_ptr<ApexHandlerInterface> CreateApexHandler();
 };
 
 }  // namespace chromeos_update_engine