lineage: add soong bits for boardflags

Change-Id: If01db1eb6b1432a6c4d26d5c9701895ab4dc3ff5
diff --git a/build/soong/soong_config.mk b/build/soong/soong_config.mk
new file mode 100644
index 0000000..d5e6de9
--- /dev/null
+++ b/build/soong/soong_config.mk
@@ -0,0 +1,5 @@
+lineage_soong:
+	$(hide) mkdir -p $(dir $@)
+	$(hide) (\
+	echo '{'; \
+	echo '') > $(SOONG_VARIABLES_TMP)