Revert "Revert "Fix filter rule when checking for apks in PRODUCT_COPY_FILES.""

This reverts commit 06b3255118ed4b92361c195dc77e6b600fe24c21.
diff --git a/core/Makefile b/core/Makefile
index 3fe0922..8bf7565 100644
--- a/core/Makefile
+++ b/core/Makefile
@@ -20,7 +20,7 @@
 # src:dest pair is the first one to match the same dest"
 #$(1): the src:dest pair
 define check-product-copy-files
-$(if $(filter %.apk, $(1)),$(error \
+$(if $(filter %.apk, $(call word-colon, 2, $(1))),$(error \
     Prebuilt apk found in PRODUCT_COPY_FILES: $(1), use BUILD_PREBUILT instead!))
 endef
 # filter out the duplicate <source file>:<dest file> pairs.