lineage: add soong bits for boardflags

Change-Id: If01db1eb6b1432a6c4d26d5c9701895ab4dc3ff5

build/soong/Android.bp

@@ -0,0 +1,7 @@
+bootstrap_go_package {
+    name: "soong-lineage",
+    pkgPath: "lineage/soong/android",
+    srcs: [
+        "android/variable.go",
+    ],
+}

build/soong/android/variable.go

@@ -0,0 +1,6 @@
+package android
+type Product_variables struct {
+}
+
+type ProductVariables struct {
+}

build/soong/soong_config.mk

@@ -0,0 +1,5 @@
+lineage_soong:
+	$(hide) mkdir -p $(dir $@)
+	$(hide) (\
+	echo '{'; \
+	echo '') > $(SOONG_VARIABLES_TMP)