Fix art-host build rule.

Use HOST_CORE_IMG_OUT, now that the image is being generated in a
platform dependent directory.

Change-Id: I5509012e9ed0d745b70b2a58227213b027227c97
diff --git a/Android.mk b/Android.mk
index 82b813a..1d42dc7 100644
--- a/Android.mk
+++ b/Android.mk
@@ -367,7 +367,7 @@
 ########################################################################
 # "m art-host" for just building the files needed to run the art script
 .PHONY: art-host
-art-host:   $(HOST_OUT_EXECUTABLES)/art $(HOST_OUT)/bin/dalvikvm $(HOST_OUT)/lib/libart.so $(HOST_OUT)/bin/dex2oat $(HOST_OUT_JAVA_LIBRARIES)/core.art $(HOST_OUT)/lib/libjavacore.so
+art-host:   $(HOST_OUT_EXECUTABLES)/art $(HOST_OUT)/bin/dalvikvm $(HOST_OUT)/lib/libart.so $(HOST_OUT)/bin/dex2oat $(HOST_CORE_IMG_OUT) $(HOST_OUT)/lib/libjavacore.so
 
 .PHONY: art-host-debug
 art-host-debug:   art-host $(HOST_OUT)/lib/libartd.so $(HOST_OUT)/bin/dex2oatd