Fix update_engine build for non-Brillo targets.

This patch fixes the build for non-Brillo targets that have dbus
enabled (the default for AOSP).

Bug: None
Change-Id: I8225a25bfd73a1c8bc55a784dcc0624213e61d47
Test: mmma system/update_engine on aosp_arm-eng and brillo targets
diff --git a/Android.mk b/Android.mk
index ea37507..6c70e12 100644
--- a/Android.mk
+++ b/Android.mk
@@ -208,7 +208,7 @@
 
 endif  # BRILLO_USE_DBUS == 1
 
-ifdef BRILLO
+ifeq ($(BRILLO_USE_DBUS),1)
 
 # libupdate_engine (type: static_library)
 # ========================================================
@@ -306,7 +306,7 @@
     update_status_utils.cc
 include $(BUILD_STATIC_LIBRARY)
 
-endif  # defined(BRILLO)
+endif  # BRILLO_USE_DBUS == 1
 
 # update_engine (type: executable)
 # ========================================================