Move AndroidConfig.h from system/core to the build project.

So unbundled branches don't need to include the system/core project.

Change-Id: Ic4ef62ee6df069b9b2dd123aed95a3e7fcdfc146
diff --git a/core/config.mk b/core/config.mk
index b35e55d..e1f49af 100644
--- a/core/config.mk
+++ b/core/config.mk
@@ -222,7 +222,7 @@
 
 # $(1): os/arch
 define select-android-config-h
-system/core/include/arch/$(1)/AndroidConfig.h
+build/core/combo/include/arch/$(1)/AndroidConfig.h
 endef
 
 combo_target := HOST_