Product configuration in Starlark support files.

Bug: 170637441
Test: rbcrun build/make/tests/run.rbc
Change-Id: Ie8f0c3dea66a287f2b0a3b588c446bfbb2c9a978
diff --git a/core/build_id.rbc b/core/build_id.rbc
new file mode 100644
index 0000000..4f33833
--- /dev/null
+++ b/core/build_id.rbc
@@ -0,0 +1,21 @@
+
+# Copyright 2021 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# This file has been manually converted from build_id.mk
+def init(g):
+
+    # BUILD_ID is usually used to specify the branch name (like "MAIN") or a branch name and a release candidate
+    # (like "CRB01").  It must be a single word, and is capitalized by convention.
+    g["BUILD_ID"]="AOSP.MASTER"
\ No newline at end of file