work around kati bug

The kati step does not seem to pass down variables used under
pattern targets.

BUG=b:26438312
TEST=building under ninja can find packages

Change-Id: I4179e8a8cb609072ad5508fc996b40ea84ae25b4
diff --git a/Android.mk b/Android.mk
index 08e41d8..b5c4088 100644
--- a/Android.mk
+++ b/Android.mk
@@ -72,7 +72,7 @@
 3RD_PARTY_EXTERNAL_DEPS += $(filter $(3RD_PARTY_EXTERNAL_LIBS),$(product_MODULES) $(PRODUCT_PACKAGES))
 
 # Actually run the emerge command for the specific package.
-%.emerge: TARGET_TO_ATOM = $(notdir $(patsubst %/,%,$(dir $(1))))/$(notdir $(1:.emerge=))
+TARGET_TO_ATOM = $(notdir $(patsubst %/,%,$(dir $(1))))/$(notdir $(1:.emerge=))
 %.emerge: | $(3RD_PARTY_WRAPPERS) $(3RD_PARTY_CONFIGS) $(3RD_PARTY_EXTERNAL_DEPS)
 	$(hide)mkdir -p $(dir $@) $(TARGET_OUT_GENTOO)/tmp
 	$(hide)emerge $(call TARGET_TO_ATOM,$@)