build: soong: put lineage variables in the "Lineage" struct

Change-Id: I9ed55cea0c55f0078f8f97ad4037b16ed11c0156
diff --git a/build/soong/soong_config.mk b/build/soong/soong_config.mk
index d5e6de9..ac7e900 100644
--- a/build/soong/soong_config.mk
+++ b/build/soong/soong_config.mk
@@ -1,5 +1,8 @@
+# Insert new variables inside the Lineage structure
 lineage_soong:
 	$(hide) mkdir -p $(dir $@)
 	$(hide) (\
 	echo '{'; \
+	echo '"Lineage": {'; \
+	echo '},'; \
 	echo '') > $(SOONG_VARIABLES_TMP)