Fix build rule.

There is no such thing as 2ND_HOST_CORE_DEX_FILES.

Change-Id: I87187267effe239c898aa504b914138e4f722a80
diff --git a/build/Android.oat.mk b/build/Android.oat.mk
index 3117f71..916fd58 100644
--- a/build/Android.oat.mk
+++ b/build/Android.oat.mk
@@ -26,7 +26,7 @@
 # Use dex2oat debug version for better error reporting
 # $(1): 2ND_ or undefined, 2ND_ for 32-bit host builds.
 define create-core-oat-host-rules
-$$($(1)HOST_CORE_IMG_OUT): $$($(1)HOST_CORE_DEX_FILES) $$(DEX2OATD_DEPENDENCY)
+$$($(1)HOST_CORE_IMG_OUT): $$(HOST_CORE_DEX_FILES) $$(DEX2OATD_DEPENDENCY)
 	@echo "host dex2oat: $$@ ($$?)"
 	@mkdir -p $$(dir $$@)
 	$$(hide) $$(DEX2OATD) --runtime-arg -Xms16m --runtime-arg -Xmx16m \